General Music Chat

I see
ok well i will try to keep that in mind.

to tell you the truth JCP, I worked avionics in the Air Force for a few years.. Schmitt Triggers/ paralell adders / counters boolean algebra stuff..and such..troubleshooting is stressful for me, causr there is a lot to it..

I will let you and Slacker figure this out, I have forgotten too much analog electronics.. thanks for sharing..

dane are you drinking?

you thought process seems very erratic.

no, I am insane.. to a certain degree

Insanity is good. Sanity is bad.

NoT? Then just look at what OUR government is doing to us.

well I guess what I am trying to decide is should I replace the 80 uF caps or install 40's as the schematics says.

looking over the chassis I would bet good money that the 80's are original installation.
and both amps have them
in place of the spec'd 40's
both amps malllory 80 MFD 450v
curious.

My 2c

I'm not a tube amp tech but I do a lot of troubleshooting and diagnosis in electronic controls. My first questions would be "Did they change anything else in the circuit to warrant larger caps?" and "Are we sure they are original?"

The benefit of larger caps from my limited knowledge is smoother DC power with less AC hum and potentially greater transient response.

The downside of larger caps is a transient response that exceeds circuit design downstream causing spike overloads and possible smoke production.

Peter Traynor is still around, why not ask him?

mmmmmmmmmmmmmmmmmmmmmmm


looking at the solder connections
if they were changed later on it could not have been much later.
I would swear they have not been disturbed at all,
esp the grounding to the chassis.
as far changing any thing else in the amp,
that will take some time to discover, but I guess I must.
if i don't it will bother me, esp when it pops or crackles
which they always do anyway.

JCP,

This schematic shows the 80uf caps for a MkII. I think that is what you have so they are original. Also the website describes this amp as "glassy tone with huge transient response, excellent for bass." That is consistent with it's design.

http://www.lynx.bc.ca/~jc/700912_YBA1_A_Mk2.gif

as you can see from the schematic
these are not tube rectifier amps
they have diode rectified power supplies
I was actually thinking of converting them back to tube recs
for the sag.

huhhuuhhuuhuhu huuhh huuh h .... He said 'rectifier..." hihhihhiheeeeehhihi

My 2c

I'm not a tube amp tech but I do a lot of troubleshooting and diagnosis in electronic controls. My first questions would be "Did they change anything else in the circuit to warrant larger caps?" and "Are we sure they are original?"

The benefit of larger caps from my limited knowledge is smoother DC power with less AC hum and potentially greater transient response.

The downside of larger caps is a transient response that exceeds circuit design downstream causing spike overloads and possible smoke production.

Peter Traynor is still around, why not ask him?

Actually, larger capacitance holds back surges. It takes time to charge a power supply cap and the larger in capacitance a cap is the less it is subject to instantaneous spikes or surges.

My 2c

I'm not a tube amp tech but I do a lot of troubleshooting and diagnosis in electronic controls. My first questions would be "Did they change anything else in the circuit to warrant larger caps?" and "Are we sure they are original?"

The benefit of larger caps from my limited knowledge is smoother DC power with less AC hum and potentially greater transient response.

The downside of larger caps is a transient response that exceeds circuit design downstream causing spike overloads and possible smoke production.

Peter Traynor is still around, why not ask him?

Actually, larger capacitance holds back surges. It takes time to charge a power supply cap and the larger in capacitance a cap is the less it is subject to instantaneous spikes or surges.

I am certainly no expert with tube amp circuits but there does seem to be some disagreement regarding upsizing capacitance and circuit reliability. In JPCs case it looks like 80uf is the correct value from the MkII schematic. He could probably go to 100uf with no issues but 160uf may present tube reliability problems. This is my understanding at least... from a supplier website:

"The old "rule of thumb" when replacing electrolytic capacitors is to not use more than 80% higher (or 20% lower) than "the original" uF size. If you replace an E-cap with one that has too high a MFD, the DC voltages will be higher than called for and your tubes and other parts will wear out faster. If you use too low a uF size, your radio will hum."

do not forget about inductance..it is related to capacitance.. it is a vital requisite in electronic circuitry/

Capacitors store energy in electric fields. An inductor does the same with magnetic fields.

JCP,

This schematic shows the 80uf caps for a MkII. I think that is what you have so they are original. Also the website describes this amp as "glassy tone with huge transient response, excellent for bass." That is consistent with it's design.

http://www.lynx.bc.ca/~jc/700912_YBA1_A_Mk2.gif

well you are right there,
I mistook the dual 40's cans as individual but i see thy are soldered together.

i guess I went with the yb1a and made assumptions when i took the lid off the Mk II
your right it is only the 50 watt that are mis labeled.