DIY tube amps

[angelod307]

Even with the schematic a mess, i just finished assembling nine tube amps without issue short of a sovtec running red as i bought them unchecked i guess. Not saying that it can not be better, but they do infact work well, just rolling a new tube in may be detrimental.

[mbskeam]

a. somebody drew a schematic on a computer
b. somebody scratched out part of the bias circuit
c. somebody drew in another part of the bias circuit in the margin on the same page
d. somebody drew something else in the margin on another page, which looks like a voltage dropping adapter

A yes=Bob C
B yes=me, wrong parts in bias, to small of a zeners, would let amp red plate.
C yes=me, new Bob C design
D yes=me, Bob C design, this replacesthe 3.9k ohm/5watt resistor on the PS page, goes between B1 and B2

1. who drew the schematic in "a"
2. who crossed off something on the schematic as "b" and what did they scratch out
3. who drew that "c" stuff in the margin
4. who drew that "d" stuff on the last page. it looks like "d" is a kludge to fix an out of spec transformer.

1=Bob C
2=me per Bob C, red plated amp with wrong zeners in place
3=me
4=me, per Bob C, yes the transformer was/is to high of a voltage, causing the amps to red plate with some tubes, running at the very edge of safe



these are MY copys to work from, ALL the designs are BOB C

[Magnaryder]

4. who drew that "d" stuff on the last page. it looks like "d" is a kludge to fix an out of spec transformer.

The original design was for 7189s, they can withstand a much higher plate voltage than the EL84/6BQ5s we had with our kits. The outcome of the zener mod reduces the plate voltage allowing the EL84s to work in the amp.

easy peasy...well for Mike. he did the zener mod in my amps. I did the boutique mods.

the thread is here.

viewtopic.php?f=8&t=17835

ray

[bob p]

thanks everybody for the help in making things clearer.

[Magnaryder]

thanks everybody for the help in making things clearer.

That;s why WE get the big bucks...and I got swamp land for sale.

Bob.....glad Mike could help.

ray