100w non-master kit keeps blowing tubes! HELP!

[Roe]

voltage readings look right (although v4 pin 4 is a little high). I assume your problem is redplating. please read the long thread about redplating I started recently (1959 w/larmar redplates).

a few tips that may remove the problem:
install a 100k on v3 grid
up the tail resistor to 100k or 47k
use 10k or 5k6 grid resistors on all output tubes
twist OT primaries and secondaries - and keep them apart (not even in parallel)
decrease the 82k to 68k

when the amp starts to redplate you need to turn down or even switch of

Wow, that was an epic thread, I think I'll need to read it a few times for it all to sink in. Thanks!

- V3 grid...do you mean just lift the wires to pins 2 & 7, attached a pair of 100ks, and re-solder to pins 2 & 7? I'm assuming this is what you meant...
- What resistor is the 'tail' resistor? My wild guess would be the 10k that comes out of where the two 1M and the one 470 resistors converge. Correct?
- Per the instructions, I have 5k6 grid resistors on all the output tubes (you can sorta see them attached to pin5 on one of my pics)...I guess I'll have to raise this to 10k and see what happens.
- My OT primaries are twisted, but my secondaries are not AND I have them all running parallel AND zip-tied together per instructions...I'll mess with that although from just looking at it, I'm not sure where else I could put them.

Alright, I'll make some changes and reply back later.

THANKS AGAIN!

- no the input of the tube (pin 2), not the output.
- yes, the 10k is the tail resistor (connected to 470 ohm)
- keep the 5k6s first, try the other things first

[d20]

Ok...so I made these changes...

- Placed a 100k on pin2 of V3.
- Upped the tail resistor to 100k.
- Decreased the 82k to 68k.
- I wasn't able to up my 5k6 grid resistors to 10k because I was out.

This seemed to help a BUNCH. Instead of taking less than a minute to start redplating badly it took a good 20 of dimed, heavy drop-d riffing to get a hint of redplating to show up. Now since I'm down to my last quad and I'm broke, I didn't want to push it. The major difference here was that it wasn't V4 & 5 that started redplating, it was V6 slight red and V7 even less. The amp does sound a bit different, but not bad.

I'm not sure if a certain level of redplating is acceptable...my gut says no, but please, enlighten me. Regardless, tomorrow I'll pick up some 10k's and see if they get everything under control.

Thanks again!

[axeman]

Check were the bias trim pot is mounted, make sure the turret that is connect to the bias resistor is not touching the other two that are wired together, if possible check the bottom of the turret board. I had a similar problem, when I removed the turret board to install a new one I realized those three turrets that hold the bias trim pot were all touching together (all three).

Good Luck

Art

[Roe]

Ok...so I made these changes...

- Placed a 100k on pin2 of V3.
- Upped the tail resistor to 100k.
- Decreased the 82k to 68k.
- I wasn't able to up my 5k6 grid resistors to 10k because I was out.

This seemed to help a BUNCH. Instead of taking less than a minute to start redplating badly it took a good 20 of dimed, heavy drop-d riffing to get a hint of redplating to show up. Now since I'm down to my last quad and I'm broke, I didn't want to push it. The major difference here was that it wasn't V4 & 5 that started redplating, it was V6 slight red and V7 even less. The amp does sound a bit different, but not bad.

I'm not sure if a certain level of redplating is acceptable...my gut says no, but please, enlighten me. Regardless, tomorrow I'll pick up some 10k's and see if they get everything under control.

Thanks again!

earlier you were driving v4-5 too hard. now you are driving v6-7 too hard. try a 47k (or 27k) tail resistor.

I ended up with 27k tail resistor, 47k on v3 pin2, and 105k/83k5 plate resistors

[d20]

Alrighty...I dropped the v3 resistor to 47k, the tail to 27k, and upped the grid resistors to 9k1. This seemed to finally do the trick as the only way I was able to get the slightest bit of glow from V6 & 7 was by playing ridiculous drop D riffs for well over 20 minutes. If I played the way I normally play (AC/DC, GnR, STP, etc..), the redplating disappeared completely.

Is that slight bit of glow acceptable or do I need to tweak until it never presents itself?

Thanks for all your help!

[Roe]

try reducing tail to 20k or 15k or reduce the 82k to 68k. this should reduce the redplating even more

[d20]

try reducing tail to 20k or 15k or reduce the 82k to 68k. this should reduce the redplating even more

I've already dropped my 82k to 68k, so I guess I'll drop the tail down to 15k and see what happens.

Thanks!