I recently repaired an Akai X1800SD R2R deck for a customer. Same issue as you're having. the main cause was dirty contacts on the record switches, and 2 bad solder joints on them. Take your time. I also would look for any kind of conductive residue on the boards. Clean any flux leftover if you see any...
I've actually already repaired this issue. There are comments around here from people saying flux has no chance of decreasing resistance between close pins and others saying that it can do. I must read up on this more: However it was when I got rid of the flux residue that this problem went away. Check out part three of this and thank you for the suggestions: ruclips.net/video/eVwQUN_M8OU/видео.html
You need the flux to create a wet joint, no flux = bad joints, I suspect that you had a dry joint. I serviced domestic appliances for ten years, If flux is getting on your contacts your overdoing it. Maddi don't know if you do this but put a little fresh solder on your iron before you de-solder it will work much better. ATB keep singing!
How did you clean the flux residue from the board/s? I have flux residue on the premp board and amp board.I did not know that it can cause problems. Thank you
Yeah, flux getting on contacts created a ton of problems for me in various devices which use high gain amplifiers, the flux creates a small resistance or capacitance between some components and it starts to oscillate. Cheers :)
Can the flux be removed? My Akai 365D has some of the same symptoms that your 260 has so I am hoping that watching your videos will help me when I tackle that machine.
tThis machine has a head switch to switch between the forward and reverse heads. They get dirty and make a motor boating sound like you hear. Follow the wires from the playback and record heads and you will find a slide switch. Inject some De-Oxit into the switch and work it back and forth a bunch of times. There is also a slide switch located on the record board and on the playback equalization board. Clean them, too.
Ahaa I already sprayed the switch on the record board but there's another one? I will have a look at that. When I turn this thing on and unplug the heads from the audio board, that constant bomping sound still remains except becomes sharper. I have some switches to find :o)
It should be behind the heads on a PCB. It's not a switch per-say but a relay. The cover needs to come off and De-Oxit sprayed on a piece of regular printer paper and drug thru the contacts. Be careful when doing this, the blocks in the relay can come loose and then you have to figure out how the leafs in the relay go. I would not think the head relay would be the problem considering the playback seemed fine before the work was done, forward and reverse play. Concern yourself on changes made and there effects on current situations.
Hi Ms Mad Lemon and my compliments for your channel! I am overhauling a GX-260D and I've almost finished my work. Unfortunately it misses the plastic head cover, I ask you if you take some measurements in orderd the draw it to 3d print one. Do you think it is possible? Thanks in advance!
@@gbclab I'm currently repairing a GX-260D. The head cover is there but partially brocken so I'm trying to create a 3d drawing for a replace. ( github.com/dimitri-rebrikov/gx260d ) The plastic window frame for the tape counter is completely missing. Is it possible that you provide me the 3d drawing for the head cover and some measurements for the tape counter frame? Thanks in advance!
Wish i could help you Ms Lemon. I have several rtr's and they are all in the process of restoration I am still learning.I have read here that you have already registered with tapeheads you will have plenty of experts there and some none experts like me haha.Hope you can get that nice looking Akai going.Best regards/Rob
Hmm It could be! Something was always loose for sure. I remember hearing crackling when it was working, switching to reverse play mode and switching back got rid of it at that time. I will try doing that, thanks!
Simon talks with experience. I would spray the play record switches with Deoxit as this could be your entire problem. Many years and many hundred of switches have been cleaned and they o not just make one noise . They can make any noise under the sun from squealing to motor boat.
I've actually already done that, (the record play switches on the record board that is) and the problem persists though I will do it again. The only thing I have left is that relay near the heads. Unless there's others.
When you spray the switches you need to exercise then 30-40 times. The spray itself will not do the job quickly. I am talking Deoxit as I can not say that other sprays will be effective or work at all. The symptom you show is most likely Rec/Play switch related. I have had older decks on the bench where all I had to do is enable the record lever- as in cassette decks, and work the record lever about 30 times and the switches would clean themselves (not long term). This then gives indication of where the problem is. This is why I buy 8 cans of Deoxit when it is on sale. I work on a lot of decks here in Chicago area.
Both issue's are at the same frequency. the needle jumps about once a second. The second clip you showed of the problem is the same but with a high frequency imposed on top. It's like a cap is charging, but is then shorted to ground. this isn't normal motorboating. Are the heads clean? First, check the relevant switches with you DMM continuity checker. Ok? Next, Without powering it up, check your power rails with your DMM when the switch is in playback. See if you have a short to ground/chassis. Click the switch, any change? Next, give the board a poke, click switches, bang it gently - any change/ the amp board is at 24v, no shock hazard. VR1 is a simple volume pot. As is VR2, this adjust's the level to the headphone's. While your at it, plug and unplug a head phone jack in and out of the socket. Any change? Check D2, which is a zener. Do you have a voltage across it? Remember to put + lead on the cathode, neg lead to anode. See if other diode's are ok, but zeners especially. They use a lot of coupling caps in this thing, check voltages across each transistor, base to emiter are they all at about 0.6/7v? are you getting odd DC reading's at the bases of TR1 etc? Lastly, get the scope on it, this will show us what is happening. First have a look at the power rail at J1 in fault conditions. Next, see what you have at 19/20- VU meter's. See if you can trace the waveform back - its starting somewhere. Try a tape with test tones. With clean heads are you getting a signal at base of TR1/2? think this through, be systematic, we'll get her sorted, no worry's. Show/record fault condition for as long as poss, same with scope pics. Service manual at Hifi Engine.
Thank you, I have quite a few suggestions here from you all and i'm going to try them starting from the simplest which is putting it back together, just in case it's shielding. I don't think the issue is with heads as when I disconnect the plug which connects the heads, the bomping remains, in fact the bomping has a sharper sound. (Part 3 of this will show that). When I get into the more complex tests i'll be getting the oscilloscope out. (I still need to break the shyness with the oscilloscope haha)
I have an oscilloscope but don't know how to use it and I even have the manual haha. I haven't found a video here on YT that is simple to understand. sigh.. The majority of the videos assume the viewer already has some knowledge.
The circuit is unstable when it does that. It can be bad electrolytic capacitors or the notorious transistors they used. There is also a problem with the glue they used that is conductive and corrosive at the same time. Take glue off the PCB. The switch contacts can also be causing the nois as in record play switches. The previous pounding sound was weird as it happened at both channels at the same time and had a regular beat- that would sound to me like the input was plugged into the output jacks with some drum type music going in. I have worked on tape decks for 45 years but Akai is one of the brands I don't bother with although I have fixed them in the past.
Yes i'm thrown back by that a little haha thank you! I have a lot of things to take note from the comments here and try. I was working on this yesterday and another discovery, which I think may be useful to mention. When the tape speed is on low, both channels are spluttering but when I set the tape speed to high, the left channel starts that squealing. It seems to be directly affected by the speed setting.
There is a EQ switch that is activated by the speed switch, this will change the way the circuit responds. what happens at slower speeds is the top end response is less and the EQ "boost" the highs to compensate. How many caps did you change? I looked at your first video and it seemed to be working fine, I would have a look at the polarity on the caps by the schematic and make sure all the grounds are clean.
Ahaa. I replaced all of them on the playback and record boards, I will check the polarity again against the manual but I know I was very aware of the polarity when changing them. Yes it worked fine before opening it however every now and then it did splutter whenever I used it. switching the playback to side B and switching it back to A helped, but in extreme cases I had to turn the power off and turn it on again and it'd be working again.
I did the capacitor thing recently on an Akai GX 270 D, relay control board. Soldered one in backwards and blew a fuse! I traced it down simple enough. It can happen for sure! I forgot how many I changed and it was the only one and the hardest to get at of course! Rest assured you'll find it, as I listen to the Dave Brubeck quartet form vinyl on a Teac A 6300, that was the first deck I restored. Keep the faith!
I would measure your power supply voltages with a volt meter. If it is not steady and/or not the right voltage that might be the problem. Are there any big electrolytic caps somewhere in the part of the circuit that is acting up? I think you already checked that by replacing those caps. BTW, a 50 volt cap will work fine. That is not your problem. How about polarity of the caps being backwards??
The polarity I double checked on each capacitor as I was replacing them one by one. the 50v cap replacing was just an act of desperation at the time.I think if It was a power issue it would also affect the amplification of the line in also...or would it? either way i'll check the power anyway. You may have a point about the bigger cap on that board, there is only one which I didn't replace, I will do that. *edit* :I just checked it and it's an inductor not a capacitor. Thank you for the suggestions Herbert!
The 2sc1312 is a very generic transistor. You can actually replace those 2sc1312 with something like 2sc2240(GR or BL) or BC550C. Although with the latter you will have to cross the legs to match the pinout. I think the 2sc1312 also came with a reversed pinout, but I could be wrong there. Easiest way to figure that out is looking at the tracks in the circuit for example the base of a transistor, say TR 3 of the recording amplifier board, where the base is connected to a 10μF capacitor. The pinout of Japanese 2sc-transistors is from left to right ECB looking at it from the flat side. So the right leg must be connected to a track on the pcb leading to that capacitor. The BC550C and most European transistors have a CBE pinout but work the same way. The 2sc711 is also a Hitachi-transistor, like the 2sc458, which also breaks down a lot and also has a reversed BCE pinout. Also made from the same unobtanium but can in most cases be replaced with a 2sc945 or KSC945C which are the same transistors still made by Fairchild. Judging from a previous video you did not have this problem before so it must have been caused by something during the restoration. I also saw you spraying solvent into those switches. The drying of the solvent in those switches could have something to do with the changing of that sound. But I would check each wire by gently pulling it to see if it comes loose. Also check if any of the screws fastening the pcb's to the frame that should make a gnd connection are actually making that connection. Also if there is a metal plate on the bottom try screwing it back on. I acts as a shielding against interference. I'm not a fan of spraying solvent into switches and potentiometers. It actually cleans very little, leaves a mess and can leave the contacts dry. It's not a good, long term solution in my opinion. It helps setting the potentiometers to the old settings but it does not guarantee that your machine is calibrated like new. Changing the capacitors for new ones which will always have a slightly different internal resistance and also aging transistors will cause the calibrationof your machine to be off. So for the best result recalibrate the machine! For an Akai it's actually quite easy to do. Anyway, keep up the good work!
Thank you! .. This actually makes the transistors less scary! Speaking of the servisol 10, what would you use for crackly pots? i've always found it useful for combating that. Before opening it up, the issue was there every now and then (rarely) the sound would splutter and also sound like someone is vigorously scrunching up newspaper. I would have to switch the deck to play side B and then switch it back again to Side A, where it would go back to normal. Extreme cases I had to turn the entire thing off, wait a couple of seconds and turn it back on. It feels as if something was teetering on edge and i've just pushed it over by opening it and tinkering with it. I will try the easiest first, as you suggested putting it all back together and see what happens, it could well be shielding as you say.
I heard that some solutions could deteriorate the carbon film of the potentiometer. I use PRF 7-78 spray. It has an image of a potentiometer on the can so I assume PRF deems it safe for use in potentiometers. The best way is actually opening it up and just cleaning the wiper with just a piece of paper. Just slide it between the track and the wiper and move it around a bit. Helps most of the time but only if you can actually safely open it. For all other cases (or if I'm lazy) I just spray it in and turn the potentiometer between it's limits a couple of times and then rince it out with the same solvent. After that I tap the excessive solvent out on a piece of paper towel before soldering it back in place again. Switches are a hole different story. I open them up and polish the contacts and spray a new layer of vaseline on them to preserve them. Works great on most vintage switches. Weird sounds are most of the time caused by transistors. Some transistors like the 2sc458 are prone to corrode. You can see the legs turning black and flakey. Apperently the corrosion can reach inside the casing. Sometimes the 2sc711 also has this problem. Also don't forget to clean the head switch. which is probably the most important switch in that machine (or any reverse machine for that matter). Judging from the service manual it's on a pcb just behind the heads.
I managed to find some 2SC945 and 2SC2240GR locally at a sensible price. i'm happy about that because from what you say they have the same pinouts as the originals. With regards to sprays, I was recommended 'Dioxit' which after reading up on it is apparently excellent, however I saw the price here, yikes! I managed to locate the head switch, one of those things that was right in front of my face except now I know what it is.
Always check the pinout if you don't know the manufacturer of the transistor and/or have the datasheet for it. Don't take my (or any) word for it! Only the respectable companies keep to the standards. I've heard about people ordering transistors and the pinouts turned to be reversed. You can buy those cheap component checkers from Ebay, which check transistors, capactors, resistors, etc. Mine also gives the pinout of the transistor you plug into it. You can also check the pinout with a normal resistance meter and measure it through like two linked diodes. The problem with those sprays is you don't know where the residu will end up. It's like washing the inside of a car by putting a waterhose through the window. Also most switches are lubricated with grease, not oil, which will also dissolve.
Yes Deoxit is a great product it cleans and lubricates.Maybe you can find it at Amazon cheaper. I don't know where you are located but here in the U.S. you can find it at electronic stores.I am shure that you can find it online also.
Double check the values of the replacement pots in the playback amplifier. ;) Also, double check that the pinouts line up correctly with the old ones. I doubt this one is the issue, though.
I think I ought to explain my reasoning. It's not because I think you would make a mistake! I see that the same fault is present on both channels. Each channel is basically identical and independent, and it would be extremely unlikely for some loose connection, broken wire, dirty switch, etc. to cause the same behaviour, at the same time in both. Various bad components could cause such oscillation, but they would surely have manifested themselves fairly clearly before the repair work. I don't think they would have degraded from usable to totally unusable so quickly, and I don't think the repair work could "provoke" degradation. I believe it's possible that a capacitor has been replaced with a defective one, or the wrong value etc, but it would have to be in some place that is common to both channels, like the power supply. Gut feeling is this is less probable. It would also be more likely to affect all functions, not just playback. Installing the wrong value of potentiometer may very well affect the stability of the amplifier as the impedance presented by the potentiometer is different, and this may affect a huge number of things, most importantly the frequency characteristics of the circuit, which is a key concern for stability. If you move the potentiometer to one extreme or the other and it makes the fault go away, this is a strong indication of it being the issue.
Also, watch out for the old trick where the value on the schematic is not the value that must be used in the circuit. This really stuffs one around greatly.
Yikes they make such mistakes on schematics? You may have a point, I know that if I turn the pots to one side (on the playback board) the issue disappears but then the entire sound goes which is to be expected I guess, im turning the signal all the way down I suppose. I will check the pots again in case i've put in wrong values. I have a suspicion with the capacitors despite them being brand new/high grade etc. Someone here suggested to try it with the case screwed back on, it could be shielding/grounding. I will try the simplest first and work up from there :o)
Forget shielding as that is hopeful guessing. The circuit should be designed to work without a case on. If there is a lose ground screw that is another issue but has nothing to do with the case. Pots do not go bad all that often and mostly due to amateurs damaging them. They can get dirty and a spray of Deoxit will fix that. No need to change them. As to schematics being different, what do you expect from a brand that gives a pretty face and sloppy design under side. This is why I don't work on them anymore as they belong in the landfill. The life time heads I have seen are all worn out. The caps are not even listed in some of their manuals. Some great company- no one else is this bad- well maybe Dokorder.
You are dealing with either a dirty switch arrangement probably like other has also said the record Play switches or a transistor or cap problem. In repair of deck is is best NOT to jump to conclusions by guessing. Connect wit the people that repair them all the time and get the truth from them. I would put in a order for KSC1845 transistors that sub for the 2SC458 that always are going bad. Change them all. Then also order a set of capacitors for that area of the board - the larger Electrolytics. Mylar and Polyester don't worry about. Monolithic or Ceramic caps are crap- replace with polyester or Polystyrene types. Mouser Electronics has all the stuff. If the transformer was bad the deck would not even power up. Also get a can of Deoxit from MCM Electronics when they are on sale. They are $9.00 then. Forget abstract ideas or concerns. You will waste time with these.
Yes I wish to try the simplest first, in this case dirty switches, I will look for the transistors and double check the capacitors but firstly it will be as you say shielding and switches.
![Как устроены швейные машинки? [Veritasium]](http://i.ytimg.com/vi/FFW0GcMCgd0/mqdefault.jpg)
The bonus track for see the complete repair serie is hearing you singing in spanish with that sweet voice. I learn a lot from your videos.
Haha thank you for your kind words Pablo :o)
I recently repaired an Akai X1800SD R2R deck for a customer. Same issue as you're having. the main cause was dirty contacts on the record switches, and 2 bad solder joints on them. Take your time. I also would look for any kind of conductive residue on the boards. Clean any flux leftover if you see any...
I've actually already repaired this issue. There are comments around here from people saying flux has no chance of decreasing resistance between close pins and others saying that it can do. I must read up on this more:
However it was when I got rid of the flux residue that this problem went away.
Check out part three of this and thank you for the suggestions: ruclips.net/video/eVwQUN_M8OU/видео.html
You need the flux to create a wet joint, no flux = bad joints, I suspect that you had a dry joint. I serviced domestic appliances for ten years, If flux is getting on your contacts your overdoing it. Maddi don't know if you do this but put a little fresh solder on your iron before you de-solder it will work much better. ATB keep singing!
How did you clean the flux residue from the board/s? I have flux residue on the premp board and amp board.I did not know that it can cause problems. Thank you
I think it might be bad resistors... I have two 260D's and i had right channel drop-outs on both, after replacing KSC1845 problem went away...
HELLO I HAVE AN AKAI GX 210D THE RELAY DOES NOT WORK IN REVERSE IT DOES NOT GO DOWN AS IT SHOULD WHAT CAN I DO TO FIX IT THANK YOU
Yeah, flux getting on contacts created a ton of problems for me in various devices which use high gain amplifiers, the flux creates a small resistance or capacitance between some components and it starts to oscillate. Cheers :)
The simplest issue was driving me nuts then, haha peopel still done believe me that flux can do such a thing. :o))
Can the flux be removed? My Akai 365D has some of the same symptoms that your 260 has so I am hoping that watching your videos will help me when I tackle that machine.
tThis machine has a head switch to switch between the forward and reverse heads. They get dirty and make a motor boating sound like you hear. Follow the wires from the playback and record heads and you will find a slide switch. Inject some De-Oxit into the switch and work it back and forth a bunch of times. There is also a slide switch located on the record board and on the playback equalization board. Clean them, too.
Thanks for coming here Warren, tapeheads unite!
Ahaa I already sprayed the switch on the record board but there's another one? I will have a look at that. When I turn this thing on and unplug the heads from the audio board, that constant bomping sound still remains except becomes sharper.
I have some switches to find :o)
It should be behind the heads on a PCB. It's not a switch per-say but a relay. The cover needs to come off and De-Oxit sprayed on a piece of regular printer paper and drug thru the contacts.
Be careful when doing this, the blocks in the relay can come loose and then you have to figure out how the leafs in the relay go.
I would not think the head relay would be the problem considering the playback seemed fine before the work was done, forward and reverse play. Concern yourself on changes made and there effects on current situations.
Hi Ms Mad Lemon and my compliments for your channel! I am overhauling a GX-260D and I've almost finished my work. Unfortunately it misses the plastic head cover, I ask you if you take some measurements in orderd the draw it to 3d print one. Do you think it is possible? Thanks in advance!
HI GBCLab, did you find a 3d plan for the head cover?
@@DimitriRebrikov yes, and done
@@gbclab I'm currently repairing a GX-260D. The head cover is there but partially brocken so I'm trying to create a 3d drawing for a replace. ( github.com/dimitri-rebrikov/gx260d ) The plastic window frame for the tape counter is completely missing. Is it possible that you provide me the 3d drawing for the head cover and some measurements for the tape counter frame? Thanks in advance!
@@DimitriRebrikov I will search if I still have the file
This noise comes from power line capacitors...DC line capacitors...electrolitic capacitors, replace all big ones connected to the DC line
Thanks for the suggestion Carlos, I've actually fixed this issue: ruclips.net/video/eVwQUN_M8OU/видео.html
Wish i could help you Ms Lemon. I have several rtr's and they are all in the process of restoration I am still learning.I have read here that you have already registered with tapeheads you will have plenty of experts there and some none experts like me haha.Hope you can get that nice looking Akai going.Best regards/Rob
The jumping meters might be dirty record playback switches. Try cleaning them and rapidly going from record to play to activate them.
Hmm It could be! Something was always loose for sure. I remember hearing crackling when it was working, switching to reverse play mode and switching back got rid of it at that time. I will try doing that, thanks!
Simon talks with experience. I would spray the play record switches with Deoxit as this could be your entire problem. Many years and many hundred of switches have been cleaned and they o not just make one noise . They can make any noise under the sun from squealing to motor boat.
I've actually already done that, (the record play switches on the record board that is) and the problem persists though I will do it again. The only thing I have left is that relay near the heads. Unless there's others.
When you spray the switches you need to exercise then 30-40 times. The spray itself will not do the job quickly. I am talking Deoxit as I can not say that other sprays will be effective or work at all. The symptom you show is most likely Rec/Play switch related. I have had older decks on the bench where all I had to do is enable the record lever- as in cassette decks, and work the record lever about 30 times and the switches would clean themselves (not long term). This then gives indication of where the problem is. This is why I buy 8 cans of Deoxit when it is on sale. I work on a lot of decks here in Chicago area.
Sam is the guru of Teac decks since he used to work for Teac and a member of tapeheads.Cheers
I went to buy a alai gx260d and after inspecting it I found that it had several problems and the heads were worn. So I did not buy it
Both issue's are at the same frequency. the needle jumps about once a second. The second clip you showed of the problem is the same but with a high frequency imposed on top. It's like a cap is charging, but is then shorted to ground. this isn't normal motorboating.
Are the heads clean?
First, check the relevant switches with you DMM continuity checker. Ok?
Next, Without powering it up, check your power rails with your DMM when the switch is in playback. See if you have a short to ground/chassis. Click the switch, any change?
Next, give the board a poke, click switches, bang it gently - any change/ the amp board is at 24v, no shock hazard.
VR1 is a simple volume pot. As is VR2, this adjust's the level to the headphone's. While your at it, plug and unplug a head phone jack in and out of the socket. Any change?
Check D2, which is a zener. Do you have a voltage across it? Remember to put + lead on the cathode, neg lead to anode. See if other diode's are ok, but zeners especially.
They use a lot of coupling caps in this thing, check voltages across each transistor, base to emiter are they all at about 0.6/7v? are you getting odd DC reading's at the bases of TR1 etc?
Lastly, get the scope on it, this will show us what is happening. First have a look at the power rail at J1 in fault conditions. Next, see what you have at 19/20- VU meter's. See if you can trace the waveform back - its starting somewhere. Try a tape with test tones. With clean heads are you getting a signal at base of TR1/2? think this through, be systematic, we'll get her sorted, no worry's.
Show/record fault condition for as long as poss, same with scope pics.
Service manual at Hifi Engine.
Thank you, I have quite a few suggestions here from you all and i'm going to try them starting from the simplest which is putting it back together, just in case it's shielding.
I don't think the issue is with heads as when I disconnect the plug which connects the heads, the bomping remains, in fact the bomping has a sharper sound. (Part 3 of this will show that).
When I get into the more complex tests i'll be getting the oscilloscope out. (I still need to break the shyness with the oscilloscope haha)
I have an oscilloscope but don't know how to use it and I even have the manual haha. I haven't found a video here on YT that is simple to understand. sigh.. The majority of the videos assume the viewer already has some knowledge.
Clean record switches and work them.
The circuit is unstable when it does that. It can be bad electrolytic capacitors or the notorious transistors they used. There is also a problem with the glue they used that is conductive and corrosive at the same time. Take glue off the PCB. The switch contacts can also be causing the nois as in record play switches. The previous pounding sound was weird as it happened at both channels at the same time and had a regular beat- that would sound to me like the input was plugged into the output jacks with some drum type music going in. I have worked on tape decks for 45 years but Akai is one of the brands I don't bother with although I have fixed them in the past.
Sam is one of the best techs at tapeheads. Seems as though we had a few folks over hear helping.
Yes i'm thrown back by that a little haha thank you!
I have a lot of things to take note from the comments here and try. I was working on this yesterday and another discovery, which I think may be useful to mention. When the tape speed is on low, both channels are spluttering but when I set the tape speed to high, the left channel starts that squealing. It seems to be directly affected by the speed setting.
There is a EQ switch that is activated by the speed switch, this will change the way the circuit responds.
what happens at slower speeds is the top end response is less and the EQ "boost" the highs to compensate.
How many caps did you change? I looked at your first video and it seemed to be working fine, I would have a look at the polarity on the caps by the schematic and make sure all the grounds are clean.
Ahaa. I replaced all of them on the playback and record boards, I will check the polarity again against the manual but I know I was very aware of the polarity when changing them.
Yes it worked fine before opening it however every now and then it did splutter whenever I used it. switching the playback to side B and switching it back to A helped, but in extreme cases I had to turn the power off and turn it on again and it'd be working again.
I did the capacitor thing recently on an Akai GX 270 D, relay control board. Soldered one in backwards and blew a fuse! I traced it down simple enough. It can happen for sure! I forgot how many I changed and it was the only one and the hardest to get at of course!
Rest assured you'll find it, as I listen to the Dave Brubeck quartet form vinyl on a Teac A 6300, that was the first deck I restored. Keep the faith!
I would measure your power supply voltages with a volt meter. If it is not steady and/or not the right voltage that might be the problem. Are there any big electrolytic caps somewhere in the part of the circuit that is acting up? I think you already checked that by replacing those caps. BTW, a 50 volt cap will work fine. That is not your problem. How about polarity of the caps being backwards??
The polarity I double checked on each capacitor as I was replacing them one by one. the 50v cap replacing was just an act of desperation at the time.I think if It was a power issue it would also affect the amplification of the line in also...or would it? either way i'll check the power anyway. You may have a point about the bigger cap on that board, there is only one which I didn't replace, I will do that. *edit* :I just checked it and it's an inductor not a capacitor.
Thank you for the suggestions Herbert!
Did it ever work then ? Hello !
Hello! Indeed it did, see the description of the video for the next part.
@@MsMadLemon Oh great ! I'm so happy for you ! Lovely machine in such good hands .
The 2sc1312 is a very generic transistor. You can actually replace those 2sc1312 with something like 2sc2240(GR or BL) or BC550C. Although with the latter you will have to cross the legs to match the pinout. I think the 2sc1312 also came with a reversed pinout, but I could be wrong there. Easiest way to figure that out is looking at the tracks in the circuit for example the base of a transistor, say TR 3 of the recording amplifier board, where the base is connected to a 10μF capacitor. The pinout of Japanese 2sc-transistors is from left to right ECB looking at it from the flat side. So the right leg must be connected to a track on the pcb leading to that capacitor. The BC550C and most European transistors have a CBE pinout but work the same way.
The 2sc711 is also a Hitachi-transistor, like the 2sc458, which also breaks down a lot and also has a reversed BCE pinout. Also made from the same unobtanium but can in most cases be replaced with a 2sc945 or KSC945C which are the same transistors still made by Fairchild.
Judging from a previous video you did not have this problem before so it must have been caused by something during the restoration. I also saw you spraying solvent into those switches. The drying of the solvent in those switches could have something to do with the changing of that sound. But I would check each wire by gently pulling it to see if it comes loose. Also check if any of the screws fastening the pcb's to the frame that should make a gnd connection are actually making that connection. Also if there is a metal plate on the bottom try screwing it back on. I acts as a shielding against interference.
I'm not a fan of spraying solvent into switches and potentiometers. It actually cleans very little, leaves a mess and can leave the contacts dry. It's not a good, long term solution in my opinion.
It helps setting the potentiometers to the old settings but it does not guarantee that your machine is calibrated like new. Changing the capacitors for new ones which will always have a slightly different internal resistance and also aging transistors will cause the calibrationof your machine to be off. So for the best result recalibrate the machine! For an Akai it's actually quite easy to do.
Anyway, keep up the good work!
Thank you! .. This actually makes the transistors less scary!
Speaking of the servisol 10, what would you use for crackly pots? i've always found it useful for combating that.
Before opening it up, the issue was there every now and then (rarely) the sound would splutter and also sound like someone is vigorously scrunching up newspaper. I would have to switch the deck to play side B and then switch it back again to Side A, where it would go back to normal. Extreme cases I had to turn the entire thing off, wait a couple of seconds and turn it back on.
It feels as if something was teetering on edge and i've just pushed it over by opening it and tinkering with it.
I will try the easiest first, as you suggested putting it all back together and see what happens, it could well be shielding as you say.
I heard that some solutions could deteriorate the carbon film of the potentiometer. I use PRF 7-78 spray. It has an image of a potentiometer on the can so I assume PRF deems it safe for use in potentiometers. The best way is actually opening it up and just cleaning the wiper with just a piece of paper. Just slide it between the track and the wiper and move it around a bit. Helps most of the time but only if you can actually safely open it. For all other cases (or if I'm lazy) I just spray it in and turn the potentiometer between it's limits a couple of times and then rince it out with the same solvent. After that I tap the excessive solvent out on a piece of paper towel before soldering it back in place again.
Switches are a hole different story. I open them up and polish the contacts and spray a new layer of vaseline on them to preserve them. Works great on most vintage switches.
Weird sounds are most of the time caused by transistors. Some transistors like the 2sc458 are prone to corrode. You can see the legs turning black and flakey. Apperently the corrosion can reach inside the casing. Sometimes the 2sc711 also has this problem.
Also don't forget to clean the head switch. which is probably the most important switch in that machine (or any reverse machine for that matter). Judging from the service manual it's on a pcb just behind the heads.
I managed to find some 2SC945 and 2SC2240GR locally at a sensible price. i'm happy about that because from what you say they have the same pinouts as the originals.
With regards to sprays, I was recommended 'Dioxit' which after reading up on it is apparently excellent, however I saw the price here, yikes!
I managed to locate the head switch, one of those things that was right in front of my face except now I know what it is.
Always check the pinout if you don't know the manufacturer of the transistor and/or have the datasheet for it. Don't take my (or any) word for it! Only the respectable companies keep to the standards. I've heard about people ordering transistors and the pinouts turned to be reversed. You can buy those cheap component checkers from Ebay, which check transistors, capactors, resistors, etc. Mine also gives the pinout of the transistor you plug into it. You can also check the pinout with a normal resistance meter and measure it through like two linked diodes.
The problem with those sprays is you don't know where the residu will end up. It's like washing the inside of a car by putting a waterhose through the window. Also most switches are lubricated with grease, not oil, which will also dissolve.
Yes Deoxit is a great product it cleans and lubricates.Maybe you can find it at Amazon cheaper. I don't know where you are located but here in the U.S. you can find it at electronic stores.I am shure that you can find it online also.
What was the problem with your Akai?
Love when you sing Mecano 😎🕺🏻
Double check the values of the replacement pots in the playback amplifier. ;)
Also, double check that the pinouts line up correctly with the old ones. I doubt this one is the issue, though.
Sure. No harm in double checking ;o)
Thanks for the suggestion!
I think I ought to explain my reasoning. It's not because I think you would make a mistake!
I see that the same fault is present on both channels. Each channel is basically identical and independent, and it would be extremely unlikely for some loose connection, broken wire, dirty switch, etc. to cause the same behaviour, at the same time in both.
Various bad components could cause such oscillation, but they would surely have manifested themselves fairly clearly before the repair work. I don't think they would have degraded from usable to totally unusable so quickly, and I don't think the repair work could "provoke" degradation.
I believe it's possible that a capacitor has been replaced with a defective one, or the wrong value etc, but it would have to be in some place that is common to both channels, like the power supply. Gut feeling is this is less probable. It would also be more likely to affect all functions, not just playback.
Installing the wrong value of potentiometer may very well affect the stability of the amplifier as the impedance presented by the potentiometer is different, and this may affect a huge number of things, most importantly the frequency characteristics of the circuit, which is a key concern for stability.
If you move the potentiometer to one extreme or the other and it makes the fault go away, this is a strong indication of it being the issue.
Also, watch out for the old trick where the value on the schematic is not the value that must be used in the circuit. This really stuffs one around greatly.
Yikes they make such mistakes on schematics?
You may have a point, I know that if I turn the pots to one side (on the playback board) the issue disappears but then the entire sound goes which is to be expected I guess, im turning the signal all the way down I suppose.
I will check the pots again in case i've put in wrong values. I have a suspicion with the capacitors despite them being brand new/high grade etc.
Someone here suggested to try it with the case screwed back on, it could be shielding/grounding. I will try the simplest first and work up from there :o)
Forget shielding as that is hopeful guessing. The circuit should be designed to work without a case on. If there is a lose ground screw that is another issue but has nothing to do with the case. Pots do not go bad all that often and mostly due to amateurs damaging them. They can get dirty and a spray of Deoxit will fix that. No need to change them. As to schematics being different, what do you expect from a brand that gives a pretty face and sloppy design under side. This is why I don't work on them anymore as they belong in the landfill. The life time heads I have seen are all worn out. The caps are not even listed in some of their manuals. Some great company- no one else is this bad- well maybe Dokorder.
reverse capacitor?
It's fixed already :o)
Me suenan esos equipos , buen vídeo , saludos
You are dealing with either a dirty switch arrangement probably like other has also said the record Play switches or a transistor or cap problem. In repair of deck is is best NOT to jump to conclusions by guessing. Connect wit the people that repair them all the time and get the truth from them. I would put in a order for KSC1845 transistors that sub for the 2SC458 that always are going bad. Change them all. Then also order a set of capacitors for that area of the board - the larger Electrolytics. Mylar and Polyester don't worry about. Monolithic or Ceramic caps are crap- replace with polyester or Polystyrene types. Mouser Electronics has all the stuff. If the transformer was bad the deck would not even power up. Also get a can of Deoxit from MCM Electronics when they are on sale. They are $9.00 then. Forget abstract ideas or concerns. You will waste time with these.
Yes I wish to try the simplest first, in this case dirty switches, I will look for the transistors and double check the capacitors but firstly it will be as you say shielding and switches.
Did you replace the frickin' ceramic caps as well?
OK
Record switches.
The word Freaking was used 30 times in this video. Lol
you actually counted? now I know you're smoking something, is it legal? lol
Touche' Lol
Hey MML
Come to tapeheads ! at;
www.tapeheads.net/showthread.php?t=49785
Hello Randall,
Thanks for the link! I've just registered and waiting for the administration to approve.