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No worries, AK is a great resource for all. If you don't mind the cosmetics, you can fit the smaller form factor caps with a thick neoprene "shim" and still use the proprietary cap holders from the factory. I would take the extra effort to obtain a "permanent" type of material for the shim...

Hey Salty, I went back and took a look at the schematic and my service notes. My memory was poor. The original filters were 12K uF, just like yours. There is a pretty stout relay on the power supply board that would take the inrush current I would think. Whether or not it would be damaged by an...

A Fair point. The original 9100 I repaired had 15,600 uF caps from the factory if I remember correctly, but I installed the Michael Percy 15K caps and they seemed to work great, even though they were slightly less in value. I would think sticking to capacitance values of +/- 10% would be a safe...

Hey Salty, Sounds like you've sorted things out. In a power supply circuit at least, you have some lee-way with capacitance values on the filter caps. Better to be a little bit high than too low. Always OK to be high on the voltage specs. Big caps like this are tricky to find these days. Best of...

Hey Neil, sorry for my ignorance, but how do I view your attachment pics? I'm not having any luck. Thanks! jrh

Well done Neil! AK is a great resource and community. All the best in your next project. jrh

Yep, 1/16" will be too big. Here's a link to a typical example of the right tool...

Hey neil, Sounds like you're really diving in, good on you!. ray offers a good tip about "solder suckers". They work well and are pretty cheap generally. I have had the mis?-fortune of putting in many hours working with the ST-140 boards. You really have to be cautious with them, so glad to see...

Too much fun ray, looks very cool!

Hey there B&K fan boys, Jose is right on here neil. ALWAYS document what you're taking out, and which-a-way it went. Trust me, you don't want a cap in backwards on power up. Current situation on my own ST-140 is all good, if just a little bit warm, but not worried at this point. I'm currently...

I'm a BK fan boy as well greg, my analog scope is a BK Precision. The thing is just rock solid dependable. I was fortunate enough to find it at a Hamfest, NOS, with the plastic screen protector film still on, for $40. That kind of find doesn't come along very often, but BK is all right in my...

Hey neil, Well, the choices are pretty dizzying out there for sure. Klein has a rep for being the go to tools for Electricians, so it probably has decent protection design. If you think you'll be poking into a 480V, 2000 Amp AC circuit sometime, then Klein would be the choice. Learnelectronics...

Hey neil, There are tons of meter reviews on youtube. For reviews of less expensive meters, check out learnelectronics. Paul reviews countless inexpensive meters. Some of the most thorough reviews of better meters happen on Dave Jones EEV Blog. I've been using two sub $40 meters from Asia for...

Thanks ray, your "devil may care" enthusiasm has been an inspiration! Best, jrh

ST-140 fan boys, update here: I am getting increasingly confidant that I am very near completion on this epic amp journey. Thanks to all of you guys for your feedback, commentary, and insight, as I have worked to get this amp back up to speed. The information has been invaluable, and perhaps...

Hey neil, jose is right on. Replacing those caps should not alter the bias or DC offset values significantly, assuming they are good to go initially, which it seems they are. That said, if you perceive the amp to be "running hot", they may not be. Monitoring these values as jose suggests, is a...

Hey neil, I tend to agree with jose about the filters, but I also found them here in case you want to browse: https://www.tedss.com/Catalog/Browse?searchString=101163UO75DD2B&inCategory=- jrh

Hey neil, They should 15,600 uF, not 156,000. But yes, those specs will suffice to locate them. It also looks like Cornell Dubilier is still making caps that should drop in size wise, but I haven't compared dimensions on those. jrh

Hey neilben, Welcome to ST-140 world. Thanks for the article link I'll check it out. I found direct drop in replacements for the ST-140's filter caps at specap. They're new and made by Sangamo, but they'll set you back about $36/each. The form factor is probably the biggest obstacle to replacing...

Good idea jose. I'll leave it as is, and test it with a CD source thru the bench speakers. They're little guys, Polk Audio RM1300's, but they do a remarkable job of reproducing the full spectrum for their size. First stop though, is putting a 1KHZ tone through the amp and examining the waveform...

B&K ST-140 update here guys. It looks like we are good to go here! Following the B&K procedure, I settled at about 190 mA of bias current and near zero DC offset on both channels. Everything is stable, no runaway current. Nothing getting too hot. Very pleased at this point. Open question: Would...

Friends of the ST-140 : Update here. It appears that the LED was the culprit on the right board. After replacing the LED,I was able to dial the DC offset to 0, and dial the bias to about 120 mA @ 118 V AC before I backed off. No worries, no magic smoke. I'm satisfied that we have proof of...

Hey jose, I hope you're right. At the time, it was difficult for me to test voltages, as touchy as the test set-up seemed to be. I needed to have a meter on that bias current full time. Your valuable insights are much appreciated in any case. I'm going to verify that the other transistors...

Hey jose, Thanks so much for your focus on my circuit in this 'ol amp. I think we're on to something here! As I studied the schematic, it was clear to me that the LED was doing some kind of "regulating" of the current/voltage of the B+ rail, so I decided to check it. As I found out , it was bad...

ST-140 right board forensic exam report here: Yes, it appears that Q9 & Q10 are wasted once again. I find I am growing weary of replacing $3 transistors on this circuit! In looking at the schematic, I decided to test the LED associated with R7, as well as R7 itself. The LED is testing bad...