Sencore SM152 Sweep Marker generator repair and demonstration
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- Опубликовано: 12 сен 2024
- I picked up this SM152 last year and finally got around try trying it out. Something is not right. Output is very weak.
Watch as I repair and then show what it can do.
This is a prelude to an in depth vintage TV alignment series.
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It’s exciting seeing those waves explained as to what they are and what’s expected. I look forward to learning more on this subject. I’m impressed that you explained this so clearly.
Very nice find Bob! The key is you have the knowledge to use it in your shop as you need it. You can work around little quirks it may have or deficiencies. Another great and interesting video.
Great video and as suspected it is more complicated then I thought hahaha
I just restored a Heathkit 0-12 oscilloscope and am starting to work on a precision E-400 sweep generator, I can’t wait to do some experimenting with
I love those Precision E-200 and especially E-400 signal generators. Fantastic old-time equipment.
Bob, thank you so much for this! This type of video is so invaluable, and very much needed! Thank you again and I look forward to the next in this series!
Carbon comp resistors are usually better than what you are experiencing. That's a huge variation and there doesn't seem to be any physical damage or burning. Must have been some surplus or bargain basement resistors. Wow.
Nice Job Bob !
I have an idea to use a Raspberry Pi Pico as a sweep/function generator suitable for TV alignment. I can probably output high-frequency square waves and go through frequencies in fixed steps. It wouldn't be as good as a continually-varying sweep but I think it might be good enough.
You'll need to get up to around 50MHz. Just get one of these devices using the all-in-one AD4350 : www.ebay.com/itm/334431677683
Thanks Bob!
As already said this kind of video are so interesting, actually are the reason why I started to watch YT. I’ll be looking forward for the nexts. Thanks for that. Question: would an HP 3585 spectrum analyzer be useful like this? As you said need to be configured but is all in one.
Seems like it would but I've never seen anyone do an alignment with a spectrum analyzer. The 3585 only goes up to 40MHz so it couldn't do the newer 44 MHz IFs or tuners.
Did a little research. You'll need to make sure your SA has a tracking generator. A SA on it's own just shows you signals already present. You need a tracking (sweep) generator to produce a signal to feed into your TV or radio.
@@bandersentv thanks for the reply. Yes HP 3585 has the tracking generator and marker facilities
15:00 can you set sweep width to zero?
18:00 second push button from left is 4.5 MHz. No tone modulation. You'd have a marker. Usually lower amplitude than the carrier. I'm sure you'll figure this out and let us know!
No, 0.3 is the lowest setting. Yes, you can get a marker at 4.5,but that would be of limited use. You want pure 4.5 with no other frequencies to set traps. It's also useful to sweep centered on 4.5 with markers above and below.
This is a great series, looking for more. I bought one of these awhile back. Still looking for an actual manual, haven't found one online (only the 4 pages you found). I haven't had a chance to use it, except to check it out with a spectrum analyzer. Seemed to work fairly well except that when switching to the UHF band, the output seemed to still be the same as the band before that -- no output at UHF frequencies. But maybe it's relying harmonics, if that makes sense? I'm very new to this kind of thing, and the insides might as well have been from an alien planet as far as I understand RF circuits.
I haven't found a manual either. I'm, sure it's using harmonics and I'd expect the output to be low. It's really pushing the abilities of something this old and relatively inexpensive.
Hi. I have a copy of the service manual, not very clear but useful to do the maintenance. So just tell me your email and its yours. Regards.
Do not use the special character.
Did you receive it?
It is temp0 ?
Hi Bob. I had one of those. In my opinion, the SM152 is the worst in the whole Sencore production. They built an All In One TV alignment generator but, as usually happens, AIO are not quite good and in this case, in order to reduce price, parts, like resistors, caps etc, are very low quality. Last but not least, markers are not crystal oscillator but tuned LC osc. which is not reliable and stable at all for the precision needed. It seems to me it was designed for beginners. Mine ended at Goodwill.
Ok, fair enough. Then what would you recommend? What device is built better, more accurate and can handle 22 and 44 MHz IF? Normally I use a wavetek 1002 or 1080 sweep gen, but they old have fixed markers at 1, 10 and 100 MHz. So I pair it with an external marker gen
@@bandersentv I just was posting my experience with this equipment. Believe me, I tried almost everything restoring it in order to have a reliable sweep gen in both bands and I spend many hours and money trying so, with no good results. I'm not a fan of AIO products. Never are "good for all". For the early TV's now I am using the Wavetek 2001. Very stable and reliable sweep gen. with external marker option. I built a "marker splitter box" and I can use up to 3 different external markers in the 22 sweep band (the sm152 needs the ext markers as well for this band). For the post 50's IF band. it's much easier. I use either the BK-415 or the Leader LSW-333 (this one is very good at the IF but no that good at VHF and UHF. For tuner adj I use the Wavetek 460, especially designed for the VHF band. I know that trim channel 3 or 4 could be enough but, why not to do the same for the whole VHF band? Thanks Bob.
Yes, 2001 is very good. I often use the slightly older 1002. I once saw one for sale with customer marker modules installed for 44MHz TV IF. Unfortunately, I lost out in the bidding.
Hi Bob. I am trying to repair the mine also. I have a copy of the service manual, not very clear but useful to do the maintenance. So just tell me your email and its yours. Kindest regards.
Thank you! bandersentv@gmail.com
Sent. You are welcome.
Did you receive it?
Yes, I got it. Thank you very much