View Single Post
  #15   Report Post  
Posted to sci.electronics.repair
Gareth Magennis Gareth Magennis is offline
external usenet poster
 
Posts: 818
Default Peavey Valve King 212



"Gareth Magennis" wrote in message
...


"N_Cook" wrote in message
...

Gareth Magennis wrote in message
...


"N_Cook" wrote in message
...
Gareth Magennis wrote in message
...


"N_Cook" wrote in message
...
only 6 months old , barged into a door apparently but owner cagey.
No
mention of what happened when powered up. 10 watt resistor
overheated
to
burn up cabling and black "candy floss" everwhere inside.
Will be a while before I can get any power onto it, schema on
elektrotanya.
But anyone know the DC ohmages of the transformers ? These readings
look
ok
, genericaly speaking
o/p primary 29.8/24.6 R

mains primary for 240V 4.4R
sec
heater 0.4R
HT 14.2R
other DC 74.4R





Saw one of these a while ago and had to hard wire the ribbon cable
between
pre-amp/power amp boards as it had arced/burnt the connectors.

One thing I particularly remember is the OPT input feed is connected

via
a
plug and socket to the output PCB and, unlike most Peavey units, it
is
possible to connect this the wrong way round. This will result in
all
sorts
of weird feedback/oscillations, particularly when playing with the
"resonance" pot on the back panel.

This amp cost me a lot of time and frustration.



Gareth.





At least the OPT wires are proper 500V rating. I ' ve now marked that
connector JIC.
I imagine your ribbon problem was initially the euro-crap solder
inside.
I've pared off the HT wire and spiral wrapped some sleeving around it.

The
wiring to the standby switch will go the other side of the main caps
not
over the replaced 400R 10W dropper that had exploded to 3 bits in the
conflagration.




I think it was actually the heater circuit that burnt the connector
contacts, though I'm not 100% sure of that.
I've seen this same burning on other equipment too, usually the high

current
PSU connectors, (Molex?).


Gareth.




I was wondering about the current rating through the ribbon for the op
heaters but they are daisy-chained and then awkwardly connected to the
pre
heaters, confusingly.
As this is only 6 months old perhaps a stock fault previously , the
ribbon
here is soldered either end




I seem to remember something odd about the heater circuit - is there not
some kind of series/parallel thing going on?
I seem to recall you can't pull one or more of the pre-amp tubes to leave
just the phase splitter and o/p valves working.


It's possible I'm confusing this with another amp, but you have just rung
a bell in my head.



Gareth.




Hmm, check the schematic here if you don't have one. (can't be arsed to
seek further)

http://forums.peavey.com/viewtopic.p...=17478&start=0


Seems the 4 o/p valves AND the phase splitter heaters are all in series.
Got that wrong in my last post - you can't remove the output valves and see
what the phase splitter is doing.

Not sure what or why is going on with V1 and V2, but I seem to recall if you
pull the wrong one, the other gets a double dose of heater voltage so be
careful.

Note also the feedback comes from the OPT output connected resonance and
presence circuit. Hence the mega problems if the OPT input is connected out
of phase.

This amp did cost me a lot of time, and it seems it is still doing so.


Gareth.