If the drive is way off, too low would be the worst, then you are basically using a 1 step instead of a 5 step shaper. The triangle wave isn't swinging high and low enough to hit the upper levels, in my somewhat hack-kneed explanation. So maybe you have a drive problem coming into the shaper.
Hmm, thats something I hadn't considered. Fudging the bias level would make up for a reduced triangle drive level.
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wrt your question on r318: There are two amps in the shaper, pos/neg. The positive side uses r310 and r313 plus a variable R317 for setting the base voltage. The negative uses r315 and r318 and variable r311. R310 and r318 connect to the +20 and -20 respectively. R315 connects to ground on the negative side. C313 and C315 are marked as electro's so you might want to check them. They stiffen the base bias voltage.
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Caps look like dipped tantalum. I have no real means of checking low voltage caps. I do have a crappy meter that will read value, but my tester for leakage was built in the 1930s and scoffs at the idea that anything can operate at less than 50 volts.
R310 sees +20.006 on the rail side and +3.111 at the junction of R310 and R317.
R318 sees -20.005 on the rail side and --3.132 at the junction of R381 and R317.
I would expect those to be a lot lower if the cap was shorted. I do see some high frequency ringing at that point on the scope when the triangle switches slope, but its about 6mv p-p.
So scope r329 junction with r225 and you should see your triangle.
R349 you mean? Doesn't appear that R329 and R225 meet anywhere. R225 and R349 do meet.
At that point, Looks about like 2.4v p-p with the function selector on triangle if I count the hash marks right.
If you meant R329 and R224, those do connect via the switch with the selector in sine mode. I get 3.6v p-p at that point with the selector in sine.
Then scope r224 both sides and again, triangle feeding the shaper.
3.8v p-p at the junction of R224 and R225. Smidge less on the switch side, say 3.7v p-p.
Then the junction of r329,r331,r333. If you see a sine wave there, then the problem is the switch.
triangle wave, 3.7v p-p.
All scope measurements done with the frequency dial at 15, multiplier on 10^3 using an x10 probe. Scope is a B&K 1540.
If not, then it would only take a few minutes to check the shaper diodes. and Q320 and Q340. Make note of the p-p voltage on both sides of r224. If you don't fix it with the above scoping, then I'll check my p-p at r224 and we can compare gain.
Diodes check OK, ranging from 0.585v and 0.611v. Most were 0.585-0.595, one was at 0.602 and one at 0.611. Transistors check OK using the diode test function. Beyond that I'd need to spend some time replicating a long-obsolete battery for my 1960s vintage Hickock 890 transistor tester. I really don't do much solid state repair and I haven't needed that thing enough to spend the time on it. In theory my tube tester will do them too, but it might be germanium only. Not really sure.
I've fixed a number of these modules. It is almost always the switches. If not, then it was because I blew something up prior to finding the switch problem. I had a voltmeter that someone must have run 100 amps through that had melted the solder off, so I guess that doesn't count. I had another that I pulled and pushed back into the TM5006, that which you don't want to do with power on. That took a while to fix.
I can guarantee nothing about how this was treated prior to it showing up here. My friend said when he got it the output was basically gone on one side of the waveform, and upon testing the voltages came out wrong at the test points so he replaced U512 and U566. At that point he said something else didn't work right, but he couldn't remember what it was. He apparently put this aside a couple years ago. It ended up here, and you know the rest of the story now.
Side question, does R260 on yours show any evidence of having been warm? This one is a bit darkened and the board under it is also discolored. Its dropping 7.14v across it, which is less than 1/4w on a 1/2w part.
Thanks for your help with this. Solid state gear really isn't my thing, so I sometimes need help working my way through it. I mostly mess with tube gear, but tube test gear for the most part is awful or just has so many functional and usability problems that I'm not interested in dealing with it. Nothing like trying to align a tuner with a signal generator that drifts off frequency every time a bird flies overhead or the planetary alignment shifts more than it deems appropriate.