Welcome to Solid State Guitar Amp Forum | DIY Guitar Amplifiers. Please login or sign up.

April 23, 2024, 04:17:52 PM

Login with username, password and session length

Recent Posts


TIP147 TO-218 equivalent for Fender Performer 1000

Started by mattbianconi, April 27, 2020, 01:21:11 PM

Previous topic - Next topic


TLDR: Where can I find the replacements for TIP147 and TIP142 in TO-218 cases now that those aren't made? Ones ordered from Amazon have shorted twice.

I have a Fender Performer 1000 that has been chugging along since I got it in '95.  Its always had the crazy loud "fizzt-POP" on shutting it off, and the background buzz whenever it is on. But these were mild issues for a 3 chord electric guitar player, I assumed all loud guitar amps just had that background fuzzy grumble and when you played notes on the clean channel they sounded clean, things on the two distortion channels sounded distorted and ncie. A friend brought over his newer amp though and it is quiet, doesn't bang when turning off.  So I read tons of forums and cracked it open to see what I could see. Since things were cheap and the Service Manual pdf https://drive.google.com/open?id=0B3nyYPooVy9baDB4LUNBV29aREE going around for this amp included Tech Notes I thought maybe making those changes and replacing/cleaning pots would fix those issues. There was a cap at C68 that had broken its solder so I also fixed that.
During this work I saw that the darlington at Q14 looked super janky with leads soldered at right angles onto the existing leads so they could reach the board. The large caps at C71 and C72 were much skinnier than the white outlines on the board and taller than anything I could find online, which I assume means they had been replaced, and the resistors at R172 and R173 were 120ohms as opposed to 100ohms that the specs showed. So this means someone had worked on this thing within the year or two between manufacture and the time I got the amp!  I thought that while I had the board out I should replace these things since I like everything looking clean and to spec. I made all the tech note changes and replaced the caps and everything sounded... well fine, same as before. Oh well might as well replace the transistors. 
Well, those aren't made anymore.  I ordered some TIP147 in TO-218 size off Amazon since they aren't on mouser and it played well for about 60 seconds before blowing one.  I was getting -40 DC on the white output wire and it was reading as "two diodes" as opposed to "transistor" according to my little testing device.  The other three, the two TIP142, and the other TIP147 read as "transistors". Replaced with another from Amazon and same thing. Fine for a few seconds then blew.
So did I get bad transistors from Amazon?  Should I suck it up and put the original one back in?  Is it TO-247 I should buy? Maybe there is something I broke earlier in the circuit that's causing a coincidental fail of the transistors? It smelled hot when it was on so maybe lack of new thermal grease made them overheat and they were actually fine? Thanks for any help. 


Here is the offending darlington that was apparently working fine but I couldn't leave well enough alone


Did you remember to isolate the transistor tab from the heatsink?


I would never buy transistors from Amazon, any more than I'd buy them from ebay.

What is wrong with using the TO247?   There should be plenty of room on the heat sink.  Might need to get larger insulating wafers due to the slightly larger size.

Not sure why change R172/173, they should run a bit cooler than 100 ohm.


Quote from: tonyharker on April 27, 2020, 02:14:16 PM
Did you remember to isolate the transistor tab from the heatsink?

I re-used the little clear plastic thing that was between the transistor and the heat sink. So... I think so but not sure.

Quote from: Enzo on April 27, 2020, 06:07:12 PM
I would never buy transistors from Amazon, any more than I'd buy them from ebay.

What is wrong with using the TO247?   There should be plenty of room on the heat sink.  Might need to get larger insulating wafers due to the slightly larger size.

I think you are confirming what I just wasn't 100% sure of.  TO247 is the equivalent of TO218.  Not until this morning did I really understand that. So I can get TIP142 and TIP147 from say mouser.com and those will be the same footprint basically.

QuoteNot sure why change R172/173, they should run a bit cooler than 100 ohm.
I'm not sure either. Elsewhere on the internet, maybe even this forum, someone suggested upping those to 240ohm but I don't know what that would change. I think they then came back and said nothing changed.


The TO247 is slightly larger than the TO218, but while some things have a row of them right side by side and no extra room, these amps have tons of space around the transistors.

Download the data sheet for each version and compare the dimensions.  Make sure the legs will fit the holes.  They may be slightly farther apart.  ELectrically they will work, and I THINK we can fit them in.

DO NOT get the smaller TO220 size.


The Amp I worked on years back I found R71 & R72 ran so hot it was de-laminating the traces.  :o
I remounted those off board and used 220R/10Watt mounted on the chassis.

100R causes CR56 & CR57 to cop a belting and overheat because of the 100R drop resistors, so larger values resolved that. The more voltage a Zener has to drop the hotter they run.
It's easy to see there is overheating as the PCB will likely be dark or even black burnt by now under those components.

Regards noise/buzz;
If the amp has been worked on before they might have missed a jumper wire that is part of a grounding circuit.
This was over 10 years back so not sure of the layout on these amps.
Sometimes a mounting screw is used to ground a PCB, if you forget the screw you can run into grounding noise problems.
The owner of that amp was so disappointed with the tone/feel I ended up building him a preamp system that bypassed the whole front panel and we only used the power section to run the speaker.
IIRC, he was even able to use the spring reverb as it comes after the FX return.
Re the main caps C71 & C72;
As long as they are the same rating then they should work the same.
Maybe they dried out as they also cop a lot of heat as they are close to the overheating resistors.
Sorry I can't be more help, but in my experience it's not a good amp design and darn hard to tweak. The Valve is useless as it's wired as a diode so not really part of the signal chain so you don't get any glass mojo.


The twin triode tube is wired as diodes, one facing each way.  The tube is really just a diode clipper, but with a tube instead of silicon.

The 100 ohm resistors each have a 47 ohm partner in series.  Those are the two 5 watts on the other side of the big caps.

The main voltage stays the same, and hte zener stays the same.  Raising the resistance lowers the current, and so the dissipation.  Every little bit helps.


Thanks all.  Going to order the TO247 and put those in place of the TO218.  Get it back functioning at least and put it to the side. I'm in a position now where a new amp isn't out of the picture so I'm not too worried about this one, only want to keep it running for sentimental reasons.


As the circuit is blowing power devices in seconds there maybe other issues that are lurking so you will need one of these;


Ok, can do. I was kind of worried about other issues too but was hoping that since it was working up until I pulled the old transistor that it was isolated to only that component. But perhaps I have created more problems than I solved.


Hey everyone, thanks for all the advice. I made a light bulb limiter and installed new TO247s for the pairs of darlingtons. Everything had been going strong now for the past week or so of playing. I had the reverb tank unplugged and noticed that the hiss-bang isn't there when turning the and off. Also the constant kind of low static buzz behind everything once you get past volume 2 remains. But I used a little patch cable to go from the effects send to return and now can get a pretty good clean volume before it buzzes if I set the effects return to 5ish. But! The key is that it's working great for me. Than you everyone for your help!