Solid state Fender Yale Reverb

[Fred G.]

Looking at the photos from VintageKiki and the comments from g1 - DId I NOT need to unsolder these, but, rather, unscrew these from the sockets, which I though were actually a part of the transistors? Shit...So they need to be pulled from the sockets that I unsoldered, then...gawd.

Happy to know that these are pretty much a "relatively" plug-in component, though.

Also, I not that the pins are located somewhat off-center, which, I guess, would be evident if the transistor was removed from the socket, then, correct?

Feeling pretty inept right now...again, thanks for your patience (forehead slap).

[Fred G.]

But I am learning a valuable lesson here, and I thank you gentlemen for your assistance!

[vintagekiki]

I would not like to discourage you.

If you are unsure of what you are doing, friendly advice is to seek the services of a nearby professional service. It will be professionally done, appropriate spare parts will be installed, the amplifier will be adjusted after the repair and believe me, it will cost less.
For intervention on the power amp, excepting to a minimum of knowledge, it is necessary to have experience and measuring instruments.

[Fred G.]

Absolutely NOT. I'm about the only game in this very small town. I had initially restricted my small basement repair shop to strictly tube gear and guitar wiring only; but now, people are asking me to at least take a stab at their solid state gear. I've been doing repair and restoration for the local mom 'n pop vintage guitar shop for a few years now. I'm retired, with a bachelor's degree in systems analysis, and I've been doing builds, mods, and repair for nearly 30 years - my point in that statement, is, that I learned how to learn a long time ago. Just, uhm, well,...never solid state electronics. I was an IT guy.

I tell my customers I'll take a stab at anything, and I'll not charge them a penny if I can't fix it myself and have to have them send it off somewhere else. I have never had to do this, so far.

My available tools include a variac, capacitance meter, DMM, oscilloscope (which I've never used in the 8 months since I bought it), home-made dim bulb tester, and home-built signal tracing gear (also yet to use that, but it seemed like a fun project).

I understand you're not trying to discourage me, and I appreciate your help. But I needed to present where I'm coming from. Failure is not an option, I won't accept that, primarily because there isn't a need to. I'll fix this damned thing, and happily take the knowledge I acquire from doing so. BTW, I was a member of this forum when it was originally called "the Ampage", joined in 1997. There is no need to be condescending. End of rant.

And, again - thank you for your help. I really DO appreciate it.

[The Dude]

A few random tidbits on transistor testing that might help:

Think of a transistor (for testing purposes) as 2 diodes- one from base to collector and one from base to emitter.

There are NPN and PNP transistors. (Again, for testing purposes) on an NPN transistor putting the positive meter lead on the base will forward bias the diodes giving you approximately .6V using the diode check function. On a PNP transitor, putting the negative meter lead on the base will forward bias the diodes giving you approximately .6V. . Reverse biasing the diodes (swapping meter leads) should give you an "OL" meter reading.

You also need to check collector to emitter to make sure the device is not shorted C-E.

I'll add: This is a very basic and simplified explanation of transistor testing. It leaves out lots of transistor theory and how the device actually works. It's meant only to make testing a little simpler.

If you're just starting transistor work, another handy little tidbit to help remember which is NPN and which is PNP: When you look at a transistor schematic, there is a little arrow between base and emitter. On an NPN transistor the arrow is 'N'ot 'P'ointing i'N'.

[vintagekiki]

I appreciate your persistence. This is the only way to learn.
We are all at the beginning start from zero.

For starters I would advise you to read and study ...

https://music-electronics-forum.com/forum/amplification/guitar-amps/maintenance-troubleshooting-repair/908839-yamaha-g100-b212-dc-offset/page3

... where it describes how to repair and adjust the power amp in the guitar amplifier.
Arm yourself with patience and perseverance and success will not be lacking.
Welcome to the club of the persistent.

[Fred G.]

Thank you, gentlemen. Your assistance is invaluable. It's getting late and I need to get to bed. I'll review the info you've graciously shared with me tomorrow, when I resume this solid-state journey. Again, thanks, and good night!

[Fred G.]

OK, I remove the two power transistors from their sockets, and re-did the following test:

https://vetco.net/blog/test-a-transi...04-12-25-37-07

Now, Both transistors are showing as good.steps one and two are showing slightly above .45 in one, above 4.6 in the other.

I'm concerned about the heat sink goop, though. It seems to have been down in the pin socket, on the one transistor. I've been advised by a friend I'm also consulting with that this isn't a good thing, and I need to clean the pins and sockets. Any preferred method for that? I'm assuming I need to order up some of the heatsink goop, as well, recommendations?

Thanks!

[vintagekiki]

OK you remove the two power transistors. What condition they are in. 2N6254 hard to find. If they are defective, replace them with 2N3773 or MJ15003.
When replacing the transistors in the output stage, some adjustments must be made before putting the amplifiers into operation. In post 21 is describes how to repair and what adjust in the power amp in the guitar amplifier.

[Fred G.]

OK, I fixed this sucker.

The problem was those white plastic connectors - the ones that clip down, with the pins and sockets - what are those formally called, should I ever need to order replacements?

I found the problem through chopstick probing the amp. Reflowed the solder connections, and all is well. It's not a bad sounding amp, for solid-state.

Next up - the owner wants me to go ahead and fix the reverb, as well. When I shake the amp, I get spring crashes, but there is no reverb effect when I play the amp, even with the reverb set at "10". There is no footswitch. Does the reverb on these amps default to "on" or "off" if no footswitch is available?

[The Dude]

The footswitch grounds out the reverb signal, so reverb should work without the footswitch. If you can hear the springs or a reverb crash when you bang on the amp, the return to the amp is working and the problem should be on the send to the tank. Check the reverb cables and make sure there aren't any open cables. Measure the resistance at the input to the tank at the RCA jack from tip to ground. If you get infinite resistance, you could have a bad transducer in the tank or a broken wire from the jack to the transducer. If you get an open reading, check the wires from the jack to the transducer in the tank.

[vintagekiki]

Check the reverb pan.

https://www.tdpri.com/threads/fender-yale-reverb.147862/#post-1767056

http://web.archive.org/web/20160204170116/http://billmaudio.com/wp/?page_id=46
_{Fixing the Reverb Tank}

[Fred G.]

Fixed! Again, I suspected those white clip-in DIP connectors, and...YEP, that was the problem. I reflowed the solder joints to each and every one of them. The amp sounds great, everything is working just fine! A great learning experience! Thank you all for your tips, tricks, and assistance!

[daxio]

Didn't want to make a new post as I just joined the forum so .. need help fixing same amp, different problem, if anyone can give me pointers ..

I have a Yale Reverb - really nicely put together. Early 80s, discrete components, solid timber. As far as I can make out the gain stage 3 uses half a 4558 and stage 4 is a 3007 for tube sound I guess. Stage 5 is master after the reverb return.

I have no sound out. Power amp section works. I made a signal probe and get life after the tone and gain circuits to R25 then dead after at the gates of the 3007. The zener only seems to be putting out 3.8V ( I think supposed to be 6.2) apart from that could the 4007 be blown? ( I lent the amp to a friend ..) I ordered some TI 4007s anyway. My other suspect is the 3007 trim pot - which seems to be putting out same voltage no matter where set (about 0.55v) ..

Appreciate any advice/pointers. I can solder, hold the schematic the right way up and not electrocute myself, but not too much more. Well I was getting some signal from grounds everywhere then found previous owner had wired the input jack the wrong way round ..

Cheers

[mikeydee77]

A new post is preferred with included schem or link as you will get more views.

I would start checking power supply volts and make sure they are close to spec.