[BrownBear]

24v DC version? or 110v AC?

110v AC

 

[AudioCats]

110v AC

bolt a wood cigar box under the P7 and use a transformer.... just use the existing connectors, no mechanical work required other than drilling a few holes in the wood.
Might not look super great but should last forever (if using a 100va transformer).

 

[BrownBear]

This is actually a great idea. I'm no electrical expert of course but I think I could do it. The thing I don't get with it is that it powers on partially, if that makes sense, like the power switch lights up on the back. But the tubes don't light up and there's no sound output.

 

[AudioCats]

the power light in the switch assembly probably only indicates the switch is on.

if you do go the transformer route you might need to add a diode bridge to turn the HV to DC before feeding it to the amp board. I don't think the filament supplies have to be DC (P8 has AC filament supplies and has very little hum)

Do you have the power supply board out? if so can you post some high resolution photo of it (both sides)?

 

[BrownBear]

I do not have it out but tomorrow I'll try and get it out and post pics. It'd be great to try and get it working again and at this point it's a paperweight anyway, can't make it any more useless lol.

 

[AudioCats]

got my P8 put back together, and one thing I think needs to be done to this design is to (somehow) directly pipe the heat from the cathode power resistors to the aluminum case. I bolted TO220 power resistors directly to the aluminum and the top case surface reaches 51C (hot spot 53C). Who knows how hot the circuit board area got with the original internal resistors (heat from the resistors will cook everything around first, before reaching the aluminum case).

I kind of wonder how this P8 survived this long, it looks to be well used.

 

[BrownBear]

Your post reminded me I have to get the pictures of the power supply board....tomorrow I'll be at work and I'll try to remember to grab the tools to take it apart. I have almost nothing at home. Also just went back through the thread and noticed someone said their P7 works when they put in one tube at a time....I wonder if that would be worth it to try and see if mine works that way? Just for kicks.

What was the deal with the P8 you have? Was it broken when you received it? I apologize if you posted it in the thread earlier.

 

[BrownBear]

Nah I tried it and it's still not working lol. I'll try and get some pics.

 

[AudioCats]

...

What was the deal with the P8 you have? Was it broken when you received it? I apologize if you posted it in the thread earlier.

the P8 was working ok when I got it. It ran too hot for my liking, especially the transformer. I am more comfortable with equipment that can run 24/7 all year round. so I took it apart and tried to "fortify" the whole thing. Details are in the DIY section.

 

[AudioCats]

... someone said their P7 works when they put in one tube at a time....

...

that one might be a 24v DC version.

 

[AudioCats]

I have ordered a P7, (110v AC version). estimated delivery date 1-22-2022.

I will investigate the switching supply situation and post info in the DIY section.

 

[BrownBear]

I ordered a P7, (110v AC version). estimated delivery date 1-22-2022.

I will investigate the switching supply situation and post info in the DIY section.

Ooh I'm very interested I'm glad you did get one lol. If it's better than the last I might have to get one of the new ones lol.

 

[AudioCats]

hmm, P7 not coming.
Got a message from the Aliexpress seller, "we are sorry that there is no stock of this product at present, so we have to ask you to cancel the order." (their in stock # shows 888)

this will be the end of my aliexpress buying experience.

the little bear P7 is now a collectors item, getting more precious every day.
Anybody got a P7 they want to sell? Send me a PM with price.

 

[BrownBear]

That sucks. Was it one of the new style ones or one of the old ones?

 

[AudioCats]

110v AC.