I’ve got another head on the bench.

[HomespunEffects]

I have a Parson 1975HW on the bench. Symptoms: loss of output, strong hum.

Turns out it was just a bad V1. Another crappy JJ ECC83S. I hate them.

After replacing it, I noticed some microphonics. Tapping it suggested it was V1. So i swapped in another. No change, still pinging at V1.

There’s a snubber capacitor across pins 1 and 3 of V1 that I’m 90% sure is the culprit. It’s a ceramic disc and I’ve always found them to go microphonic so i avoid them if possible in pedal builds and I tap test them at install. Do you swap in another ceramic disc and just hope it lasts a while or do you swap in something more durable? Have you found a brand that doesn’t tend to become microphonic? It is 100pF 1kV so i don’t really have a choice but to stick with ceramic so it’s probably just going to come down to brand quality. All my current stock is low volt stuff for pedals.

 

[Humbug]

You can use pretty much anything as a plate-cathode snubber. I'd just put a decent film cap of some sort in and call it a day. 1KV is not needed, 630 or 450 should be fine in that position.

 

[HomespunEffects]

You can use pretty much anything as a plate-cathode snubber. I'd just put a decent film cap of some sort in and call it a day. 1KV is not needed, 630 or 450 should be fine in that position.

Yeah, I figured that any value above audio range would also be ok.

 

[SillyOctpuss]

Can we have some pics too? I love amp and pedal gut shots.

 

[HomespunEffects]

Can we have some pics too? I love amp and pedal gut shots.

It’s a Chinese knockoff. I’ll get some pics but I can’t suggest buying one. It sounds great but the parts are cheap. I’m mostly concerned about the cheapie transformers.

 

[SillyOctpuss]

It’s a Chinese knockoff. I’ll get some pics but I can’t suggest buying one. It sounds great but the parts are cheap. I’m mostly concerned about the cheapie transformers.

I just like looking at gut shots tbh, doesn't matter if they're from budget or high end 'booteeky' gear. Gut shots are much more interesting than pics of the outside IMO.

 

[HomespunEffects]

I just like looking at gut shots tbh, doesn't matter if they're from budget or high end 'booteeky' gear. Gut shots are much more interesting than pics of the outside IMO.

It’s kinda nice looking for a knockoff. I’ll get some pics when i get back home.

 

[HomespunEffects]

I just like looking at gut shots tbh, doesn't matter if they're from budget or high end 'booteeky' gear. Gut shots are much more interesting than pics of the outside IMO.

This is the problem cap:

Anywhere you see these blue metal film resistors, I changed them last time I had it on the bench. I had to change the bias by a lot as it wasn't even close to being correct from the factory.

This resistor is the one that replaced the original one that actually caught on fire. You can still see some of the charring on the eyelet board.

 

[HomespunEffects]

And here are the cheap transformers that worry me a little:

These wires don't look stout enough for the current requirements:

 

[SillyOctpuss]

And here are the cheap transformers that worry me a little:
View attachment 41441View attachment 41442View attachment 41443

These wires don't look stout enough for the current requirements:
View attachment 41444

Yeah they're not great looking. Are you thinking about changing them?

 

[HomespunEffects]

Yeah they're not great looking. Are you thinking about changing them?

No. I’ll wait until they explode.

 

[SillyOctpuss]

No. I’ll wait until they explode.

Now that's a video I'd watch.

 

[HomespunEffects]

Ok. I got to actually diagnose the issue. It’s not the snubber cap. It’s the wire that goes from the volume pot to the grid (pin 7). I’ll replace it with a shielded wire and go from there.

 

[HomespunEffects]

I replaced the wire with a shielded wire and it fixed it right up! It actually sounds really nice. It may be worth dealing with the constant repairs.

 

[HomespunEffects]

Here’s a picture of the bad tube on the left with a fresh tube on the right.