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@@MikeGervasi i read everywhere that ground should not be connected. So i didnt even try. But any way trying would be no harm.

Hallo!!, thank you for your comment. I just chose a free youtube tone with enough low's (bass) and high's (hats etc). I have 2 A77s but I would not be so intrusive on them. They look good enough to me the A77 playback boards. I would use these boards on a machine with no original or with destroyed original PB preamps (to make a very old machine usable for example) or on a DIY project. Although they seemed to have an amazing result I would not use them in place of an original factory PB amp that is working. Cheers 😊

I think the hardest is the mainboard (the board where the cards slot in). I have not done it yet and thinking of doing it with video to help others. The PS board with the info in this video looks straight forward.

depends on how hot. If the room temp is 30oC then they normally get hot. If working without tape they are quiet then possibly its fine but not for sure.

Mobil DTE Oil Heavy ISO VG 100

The 2 CC pins are maybe for the erase head instead.

I also tried but did not succeed with recording. I don't know why. Even without erasing head there should be something recorded but no. I have not found the solution to that.

@@dchatz Im going to try on a cassette tape when I receive it.Maybe it will work.

@@monsieurturgeon4236 good. I d like to know the results

@@dchatz OK, as soon as I receive it, I will share the result.

@@jamesten thank you too

Cassettes during the 80's developed so much with dolby-c, Cr-type etc that combined with the much smaller size and convenience (threading etc) drove all consumer market to them. It wasn't just an opinion. It's the actual data (frequency response, s/n ratio etc) that showed that they were capable to take the position of the reel to reels. It's the same as today that cassettes are so much obsolete when spotify (and other such) offers the total music industry in your pocket. Messing with reel to reels starting from 1990 until today is just a hobby without any practical use and I know it. Me and some other hobbyists (like you obviously) are just keeping it for an inexplicable reason that the vast majority cannot understand. And I also understand this very well.

Convenience, pure and simple. Storage, use and after time, sound quality. R2R always had the S/N advantage, but simply put...you couldn't take it with you.

These things took up so much space though. I left a cupboard full of R2R tapes at my folks place when I emigrated, goodness knows where they ended up or if they were ever played again and what the new owner thought of their content if they were, there was everything from recordings of Radio Caroline, to program tapes for my own pirate radio station, to recordings of my Triumph motorcycle roaring past the house at full click, I'd love to hear them again myself actually.

@@dchatz Nice machine. There's something hypnotic about watching the reels go round and round. I've never owned a reel to reel but used a Revox in high school for theatre sound effects. Y

@@yamakawa511 This is a big reason to justify the messing with reels to reels. And when asked "why do you do that, it's pointless" a have a simple answer "I like looking at the reels turning".

Unfortunately there is. For my home amateur specifications, it is acceptable. It only comes down to how accurate the workshop's lathe is. The less tolerance there, the better the results. I had to try twice (seen on the video) to get an acceptable result. If anyone tries this, it must be very clear to the store that tolerance must be to the bare minimum. Better to make it a bit bigger (say 9.10-9.15mm) to be able later to take out some material in case it not very well made. Speed is adjustable so diameter accuracy is not that important.

Front bearing is sintered. Just oiling with mobil dte heavy vg100

ευχαριστω!!

It's Revox automatic information system for pointing out that brake tapes are rusty 😂

(scb=speed control board, I guess it was NOT replaced in the past and you have the non-IC type) Looks like the scb is not controlling the speed of the motor and the motor runs at its highest speed. A full recap of the scb is a first step (if you are lucky this might be enough). But it is not sure it will fix your problem. You will have to check if the tacho head is working. Put a scope on the leads (brown-blue) of the tacho head (on the scb) and see if it reads something. Check also the distance of the tacho head from the motor. Next step, check main transistor, check full bridge rectifier (have heard of some look like working but under load they don't, replace anyway. Replace the trimmer also. Check voltages on test points as per the service manual. The scb can be easy pulled out, check my other video where I do it on camera.

@@dchatz thanks i will test what you suggested. my board has ic's.

@@lito3481 If you have the IC version on a mk2, your board has been replaced in the past. Since the 555 IC has a base and can be easily replaced go on and replace that too (it is cheap).

@@dchatz i checked the tachometer with scope ,and dmm.readings are within spec of service manual.800hz & 1600hz , 500 ohms.i think i found the culprit ! the trimmer pot is very old ,the contact on the adjuster has broken off.i read on a forum that this trimmer pot will cause hyper speed on the reels if it is damaged.regardless i will recap,and install new trimmer pot thank you for you help.

Thank you

Αθηνα.

I have closed the machine and have given it to friend now. I'm sorry but I don't remember much about it any more. I remember one belt right in the middle but I don't remember how the take up reel moves.

Ok,thanks. Greetings from Poland

I would say Panasonic is OK. Other brands (WIMA??) are OK also. Pay attention to the specs, 0.47uF, 250V (or higher), X2 classification (don't forget that).

But i did exactly that. i lifted the motor to a new position. I even show exactly how i did it.

@@dchatz my apologies- I didn't get to that bit! 😞

@@jonvincentmusic the man apologized so lets just forget about it.

Literally 3/4’s of the fekking video is about how he adjusted the motor mounts to correct the tape path, but nah why watch the video when you can just try to be a smartass instead.

@@dchatz thanks. & he's deleted his comment & fcked off without apologising himself. 😂

Maybe I have heard of that also but the thing is my oscilloscope is 100MHz capable which is way beyond the 20KHz upper level of human capability. Even bias signal is normally about 100~150KHz which is still low enough. So I cannot find any proper reason for a digital oscilloscope with proper frequency specification, not to be suitable for analog audio devices.

​@@dchatz I do agree but they say the digital oscilospoce is slow. I don't have one, so I can't understand it. I would like get a chinese 2 channel osciloscope like yours.

@@MateusMachado go on and buy it. It's more than enough. The calibration process with it works without any problem.

​@@dchatz alright, I will do it. Thanks for your advice.

I'm to embarrassed to admit that I don't remember exactly. Looking at it, I think they indicate signal tracing points on preamplifier stages. If you look the schematic I have the signal path with a green line from heads to line output (excluding bass, treble and route to power amplifier) starting from C7 up to C42.

@@dchatz Ah, I see, thanks! Yeah, this recorder is driving me insane ahah. Almost all the voltages are good, until I put it in stereo/recording mode (push recording button in + put it in "pause") as per manual. Then the only healthy ones are on the power supply board ("healthy" is a generous word tho, for example the 40v across the c17 cap are actually 43) 😭

@@dchatz Hello there sir, bit of a follow-up, had a quick question. So, I just remembered that the recorder arrived with the voltage selector set to 240 volts (from Germany). I'm in Italy, here it's 220, so I've set it to that. Now, most if not all voltages are off compared to the tech sheet, and are mostly higher. I've set the voltage selector to 240 and 250 just to test - at 250 most are pretty much exactly what the tech sheet says. I've excluded power supply board issues (first capacitor and two bridge rectifiers) and the transformer, they are all good. My question is, if you remember/can verify of course - what did you set the recorder to when measuring voltages? And also - is it normal for even the first components in the chain reading voltages that are slightly off, even after replacing them? This is my first time ever owning AND fixing a vintage device like this, so I apologize for a stupid question ahah. Thank you so much!

@@SkaR 220 or 240 setting should be fine. Here in Greece now the official mains voltage is 230v so many suggest to put it in 240v. Check if your mains voltage is actually above 220v since that looks like to be the case. I did not do any voltage checking on mine. I first checked if signal was out of the head preamplifier and found none. Then I checked if power was going to the head preamplifier and also found none (shorted cap). I then checked caps of the head preamplifier and found couple dead. After replacing all of them everything returned to normal and I did not check further. Please note that I'm not an electricial nor even a similar proffesion. Everything I know is out of years of self learning and I do it as a hobby for reel to reels. So I may not be able to give very detailed info.

@@dchatz Aaah I see I see. Well, thank you regardless, this is still good info!

Doing bias adjustment doesn't require a test tape because it messes with the record side. The test tape is required for the playback side. If you don't have a test tape you can adjust the azimuth and the playback level by using an already known good recording as a test tape. Won't be accurate but may be OK. There is also a way to adjust azimuth by recording and flipping the tape on the back side. Google it. I have done many bias calibration by ear. If you get correct treble response it's good. But note, that is not a professional way.

Maybe I should. If the machine was mine I would, even if it wasn't necessary. The machine worked fine, that is why I did not go further. After all, doing more stuff I would risk damaging something that I couldn't find. This repair was a favor to a friend and I didn't wanna risk doing things maybe worse. Working in your living room is dangerous sometimes to do stupidities if you do more that absolutely necessary.

The last weeks I’ve made big service on my Revox A 77 mark III with all the parts from Bosch Trading Germany I ordered at. Mr. Erwin was also very helpfull in certain questions. A big adventure to do.., but now I need to calibrate it I’m desperate to find a service manual for this. Your movie of serving this machine had helped me a lot. Thank in advance.

@@ronaldbuskens3619 get the service manual from hifi engine. Other places too. You dont need to be desparate. Its easy to find.

£

Check the tacho sensor. First check the distance from the motor. Then the connection to the board. Then the frequency it registers. I have heard that if the tacho sensor is not registering anything the board goes to max speed. The service manual has certain checkpoints and voltages. Look for the schematic of the old board since most downloadable service manual show the newer IC board. I guess you have the High Speed version since the NS version may go faster when faulty but not more the 15ips. Check if the speed is within limits and can be calibrated from the coil (T201). Check if the coil has a core. Sometimes they are lost or broken from previous attempts.

Why?

@@dchatz I want to own it

Yes, you are right. That is just screwed in and can be brought a bit to the outside by adding a thin washer behind it. Don't know how it can be put further inside if that it what needed.

Thanks it helped me out heaps.

Thank you

Dont really know. I have bought many from aliexpress and i just put the most suitable one without measuring it. Sorry

Use 60 glycerol and 40 white spirit. Watch the time to get it just right.

@@HowardJohnstone there is the pit in the rubber ring- it was engaged for last ~30 years. And now it jumps at that point.

@@kaunomedis7926 A lathe must be used to remove it from the wheel.

Tested recording and works fine. I have another video with recording operational

Yes, this is the normal operation of this deck

It worked after that and still works. But i could always be wrong.

@@dchatz sorry but instructions said so. I have had 10 same and never had any problems with noice - noice comes from rubber parts normally. To open motor is big risk to most of the people. One Japanice took motor away for to place belt - its not necessary - I did not see yours but anyway easy to but.

Noice comes from rubber wheels.

@@dchatz you are doing well.

Just cleaning did not fix it. And applying silicone on the tape path is by some people considered a good thing. I have read post on forums from people applying this on tape paths to renew them. Dont know if this is a good thing. But after that, recording on this tape was perfect.

​@@dchatz I did it also and it wont cure the tape issue, only reduce the issue. What type of silicone do you use? Almost 100% the Scotch tapes do have this squeaky issue.

@@MateusMachado its on the video. Its 100000cSt (viscosity). I also tried applying it on the tape guides. After cleaning them. It makes them slippery.

@@dchatz Alright, thanks. I bet the viscosity is the key.

@@MateusMachado I used specifically the type 100000cst. I think this is crucial. Otherwise the silicone will just wipe away very quickly. The key is that the silicone sticks on and remains there

Have it since decades. I really don't know now where to find it.

check on Aliexpress for "1/4 transparency leader tape". They sell it