Sencore SM152 Sweep Marker generator repair and demonstration

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.

[dontknowbrian]

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.

[greggsvintageworkshop]

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.

[alexinnewwest]

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

[soundmankreek]

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!

[randyabgo]

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.

[eDoc]

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.

[johnnytacokleinschmidt]

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!

[mymessylab]

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.

[sorcererstan]

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.

[richardmiranda]

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.

[Joseradiola]

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.