# Phoenix Gold EQ repair



## nutt7 (Nov 15, 2015)

Hello!
I have a PG EQ215x that I picked up awhile ago. It’s physically in great shape but does not turn on. When I popped the top, I noticed the iron top was off the coil...it appears to be the upper half of an iron core for the coil. Not sure if that would cause any turn-on problems. I reattached it and it still won’t power up. I’m guessing the issue is in the remote turn on circuit. Nothing looks bad at all on the board. Edit: I did notice the two resistors have browned the board a tad in the picture. Power and ground signals seem to make it to where they are supposed to go on the supply side.

I heard that PG never released schematics so I’m wondering if anyone has any insight. I’m decent at troubleshooting and repairing, but mediocre at best without a schematic.

Any help is appreciated!


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## bnae38 (Oct 3, 2015)

I repaired one a few years ago and managed to get the power supply schematic from someone on another forum.

The one I fixed also had the ferrite case off the transformer, I actually had to buy a new top for it.
Iirc, the power supply transistors were cooked/shorted.

Lmk if you want the print I have.


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## nutt7 (Nov 15, 2015)

bnae38 said:


> I repaired one a few years ago and managed to get the power supply schematic from someone on another forum.
> 
> The one I fixed also had the ferrite case off the transformer, I actually had to buy a new top for it.
> Iirc, the power supply transistors were cooked/shorted.
> ...


I would absolutely love it if you could pass that along. If you remember where you found the ferrite case, that would be great too. I still have it so hopefully reattaching with RTV or something will be sufficient. Thank you.


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## bnae38 (Oct 3, 2015)

Pm'd.

If you have the oem cap to the transformer, just epoxy it back on. I liberally attached mine with a strip of epoxy over the whole thing.


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## bnae38 (Oct 3, 2015)

Yeah red rtv would work too.


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## nutt7 (Nov 15, 2015)

bnae38 said:


> Pm'd.
> 
> If you have the oem cap to the transformer, just epoxy it back on. I liberally attached mine with a strip of epoxy over the whole thing.


Thank you, I got the document!


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## nutt7 (Nov 15, 2015)

bnae38 said:


> I repaired one a few years ago and managed to get the power supply schematic from someone on another forum.
> 
> The one I fixed also had the ferrite case off the transformer, I actually had to buy a new top for it.
> Iirc, the power supply transistors were cooked/shorted.
> ...


Thanks again for the schematic. I was able to diagnose it pretty quick. The first transistor wasn’t doing its job (partially blown through) so I found a replacement and now the EQ works great!


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## nutt7 (Nov 15, 2015)

I may have celebrated too soon. I gave it a good 20 minute listen at moderate volume and it shut down. It MAY have sounded a little fuzzy towards the end. The transistor blew again. The transformer and the power supply area was pretty warm. I do have another transistor to pop in, but obviously something else is causing an issue. Any ideas? I suppose I can check voltages, otherwise I can throw parts at it. Any ideas?


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## bnae38 (Oct 3, 2015)

Did you replace both fets? Always want to replace all of them with new to ensure proper matching/current sharing, using the same date code parts.

I kinda threw the works at mine when I fixed it.. new sg3525 controller, new fets and the updated 100ohm gate resistors. I also devised a way to gap pad the fets to the case to heat sink them a bit too actually... Lol


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## nutt7 (Nov 15, 2015)

bnae38 said:


> Did you replace both fets? Always want to replace all of them with new to ensure proper matching/current sharing, using the same date code parts.
> 
> I kinda threw the works at mine when I fixed it.. new sg3525 controller, new fets and the updated 100ohm gate resistors. I also devised a way to gap pad the fets to the case to heat sink them a bit too actually... Lol


I did not replace the FETs. They came with somewhat of a heat sink that kind of slips over it...not sure how effective they are! I did read that if the 3525 or FETs not oscillating correctly, the 12v supply to the transformer will just heat it up. That would explain what I felt (and perhaps why the ferrite cap separated) and the heat marks at the 10 ohm resistors where they tie to the 12v supply and transformer primary. Not sure how that would cause the remote transistor to fry though. I can order some replacement parts as well and see how it goes! I will also add the gate resistors…you said you skipped the mod illustrated on the secondary side, right?


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## nutt7 (Nov 15, 2015)

I actually read my circuit board against the schematic. I’m on revision C and they’re on H. I got a few parts to swap out!


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## bnae38 (Oct 3, 2015)

Yeah, I would not do the snubber mod on the secondary like I said. It ran stupid hot.. didn't seem worth it to me.

Good luck


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## nutt7 (Nov 15, 2015)

So I completed all the revisions: replaced the p222 FETs with the ones in the schematic with upgraded heat sinks, took the rail capacitor upgrade an additional step to 35v since I had them, replaced the zener it called for, changed the sg2525 with sg3525, changed the 47ohm resistors to the FETs with 100 ohm, and swapped the 10ohm resistors and capacitors that split the primary on the transformer. The capacitors both cracked upon removal to test. Glad I ordered some.

But it works! I hope it lasts. The transformer is hot, the remote transistor that originally blew is pretty warm, the 10 ohm resistors by the transformer are damn hot (can’t touch for over one second) and the FETs are pretty warm. Capacitor c1 is warm. Not sure how hot any of these should be. Guess we will see if it dies again…any ideas or opinions welcome.


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## bnae38 (Oct 3, 2015)

Hmm, that rtv job isn't what I had in mind. Might be the reason for the heat.

Having the upper and lower core touch and form more of a continuous core is going to be more ideal.

I meant for you to "wrap" the top core in place with rtv.

The separation is going to cause the core to not perform as expected.

Then again I can't really tell from the pic, maybe the top core is pretty tight to the bottom one? Either way, don't really want insulating material between the top and bottom.


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## nutt7 (Nov 15, 2015)

bnae38 said:


> Hmm, that rtv job isn't what I had in mind. Might be the reason for the heat.
> 
> Having the upper and lower core touch and form more of a continuous core is going to be more ideal.
> 
> ...


It’s a VERY thin layer, even though a little oozed out. It’ll be a razor thin layer inside. I even carefully put a small clamp on it to keep it seated. I figured it wouldn’t effect the iron core’s ability to make a magnetic field. Think it could? The resistors concern me though. I noticed the legs were thinner on the replacements, despite having the same rating


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## bnae38 (Oct 3, 2015)

Oh the 10ohm snubbers, yeah they'll run hot .


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## nutt7 (Nov 15, 2015)

So everything was great for a month. Then my speakers made a horrible noise and the q1 transistor blew again. I soldered in another and it got very hot, very fast. My digital thermometer isn’t quite designed for this but I could see flashes of 250-300 degrees F! It smoked a little, but the music kept playing. I pulled remote power and it stayed on. Why would it get so hot? I checked the base resistor and it is all good. The FETs were hot (felt hotter than usual operation, especially considering the low volume), c1 was pretty hot too. Transformer felt normal. I feel that the 2a fuse should blow first…any clue? I’m half tempted to remove the transistor and jump the e-c to see what happens. I don’t understand why it would work great for a month then do the same thing as before.


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