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Sir, you linked to the KSA992. As I said I was looking for KSC1845FBU https://www.digikey.com/products/en?keywords=KSC1845FBU

It was the KSC1845FBU I was looking for. They have the part number, but none in stock. That was what I meant.

LOL, I figured it might be something like that. Too late! I ordered the FTA's. I only needed 4. Even with the caps I ordered, the shipping was half of the total order.

Good advice, I'll pay close attention to the pin configuration. Yeah, I saw a thread where the FBU was recommended as a replacement, but I don't really know what the differences are. I first searched Digikey for the FBU but didn't find any.

I went ahead and ordered the KSC1845FTA/KSA992FTA pairs, since they had the same gain of 300mA. Just let me know if I screwed up I guess.

I'm about to replace the transistors on the tone board of a 2226b, and I'm shopping for replacements for the 8 transistors on the board. In place of the 2SC1681 I'm going to use KSC1845's that I've found at Digikey. For the 2SA841's I'm going to use KSA992, but Digikey shows 3 choices for...

The amp is 23 years old and I knew the caps were going to fail at some point. I wanted to do some preventive maintenance and make sure it would sound its best. I also wanted to have some fun learning how to recap, and this was an easy one to do. As it turns out, one of the caps I pulled out...

That right there is my biggest problem. I don't understand schematics well enough to even know where to begin or what I should be measuring, and I've never been good at equating what I see on a schematic to what I see on the PCB. I need some learning. Youtube videos are helpful but without...

I desoldered 3 of the output MOSFETs and tested them with my multimeter. No duds found.

Attached are the service manual and schematics.

I've checked and double-checked, and as far as I can tell all the wiring is correct and connectors tight. But obviously something's wrong, and I assume I'm responsible. I doubt if anything would surprise me though :rolleyes: I can't do any more testing as the amp is taken apart and I'm not...

Oh, and as for the rail voltages, I'll have to double check those after I get the thing back together. Any recommendation for a good but cheap transistor tester? Can the output MOSFETs be tested without desoldering them?

The PCB wiring is correct, as the left and right side are mirror images. I took pics and a video of all the wiring in the unit before I ever removed anything, to make sure I put it all back together correctly. I verified this again last night. The left and right amp boards are identical, but...

I removed both amp boards and checked resistance between the transistors and the heat sink. On the left side, all had infinite resistance. On the right, 9 out of 10 had infinite resistance but one of them showed 16.2 Ohms. So, since the left side output checked out OK even though it's the...

I forgot to post my measurements. After warming up for 10 minutes at idle: DC output: Left -6 vdc, Right 0 vdc AC output: Left .357 vac, Right 0.013 vac 60V rail: Left 155.1 vdc, Right 155.0 vdc 73V rail: Left 151.7 vac, Right 180.0 vac -- significant difference. Is this bad? Left and...

OK, here are some pics under the hood. I've double-checked capacitor orientation, and they're all correct. The 8 black/white ones on the PS board in the center are obviously all pointed the same direction, same as the ones they replaced. The original spec for these is 1000 uF, but I upgraded...

Nope, one toroidal transformer. I should also mention that after I finished the recap, I set the bias and DC offset on both channels to within a hair of perfect.

So I just recapped an Adcom GFA-5500, and I've got a problem. There's a loud buzz coming from the left channel. The right channel is quiet. I made a video: There's no noise from the amp itself; it's just in the speaker output. I confirmed the problem with a second set of speakers and an...

Thanks mbz. Those are the same pots that are in there now. I have another 5500 with the same pots in it so I know they are original. BTW this other 5500 has nearly perfect DC offset so I don't dare touch the pots in that one. Some Google searching of the issue has revealed that others in the...

I just picked up an Adcom GFA-5500 amp. DC offset according to my DMM was about 55 mV on one side and 65 mV on the other. So I'm trying to adjust both sides to +/- 10 mV per the service manual, but as I turn the pot the values are jumping around wildly. They can go from -20 to +7 to +35 to...

Oh, I see. Good tip, thanks!

Interesting. Neither of the 545 II's that I'm looking at have TO-92's on the boards like the one you're showing. I checked both of my 5500's and they don't have any sinks on the boards either, unless they're a different kind that I'm not recognizing.

A-ha! That white stuff must be thermal tape: https://www.amazon.com/Ceatech-Thermal-Conductive-Adhesive-Cooling/dp/B075F37SQG/ref=sr_1_1_sspa?s=electronics&ie=UTF8&qid=1527894470&sr=1-1-spons&keywords=heatsink+thermal+tape&psc=1 Looks like it's used in place of heat sink compound.

Yep, there are heat sinks between the transistors and white pads.

I'm not sure what those white things under the transistors are, but they are very thin, like teflon tape. A very gentle prying with the edge of a sharp knife popped the transistors off, so I won't have to desolder them thankfully.