resoldered that whole part of the board.

checked voltages:

pin 1 - ~200VDC
pin 3 - ~22VDC
pin 6 - ~400VDC
pin 8 - ~22VDC

the resistances of those plate resistors are looking alright - except that r51 and r52 are both reading around 108K - when r51 should be 91K. is that difference crucial? by the looks of it, someone has changed r51 before. should i remove the board and test them out of circuit? r51 is dropping ~200VDC and r52 drops almost nothing.

orange to black: ~300VAC
orange to red: ~50VAC

orange to black: ~30 ohms
orange to red: ~10 ohms

heater to ground: ~<10 ohms

orange to ground gives me ~230VDC, like i said, but my meter reads 500VAC. i know its probably getting confused by for whatever reason putting a cap in series does not work - it reads 0VAC when i do that....

when i read orange to black of secondary i get ~320VAC.

ive tried another tube(s) and resoldered that socket.

both heaters are lit (im pretty sure - just two little glowing points on either side of the tube near its socket - the two preamp tubes and the PI are all lit up like that - that's the heaters, right?).

resoldered power tubes.

the clean channel sounds good, actually, except it gets kinda congested when it starts to break up.

but the drive channel still sounds really bad. hollowed out and totally unclear.

i get ~200VDC on pin 1 of the PI and ~400VDC on pin six. so thats bad. should i check the resistors feeding them, coming from point Y on the schematic?

whoops - i was measuring DC on the heaters by accident - yes, ive got ~6VAC there.

the brown wire gives me ~30VAC to ground
the orange wire gives me ~230VDC to ground

the PT is, in fact, TG9875.

nothing on the bottom of the turrets.

QuoteYes Black and Red B+ voltage. He says two browns are Bias voltage 34v and white is the ground. I see on yours brown as a ground on the secondary. So you have 2 browns(bias windings?) 1 orange?() 1 black(B+) 1 red(B+) and 2 Green(filaments) on your secondary right? Really just posting all this info up for points of reference and clarifications.

that sounds all right to me!

G1's idea - that the bias winding is bad and that the voltage is taken from the bridge instead - seems to make sense maybe....

one of the secondary brown wires is connected to ground and the other one to nothing.

okay ive made some progress:

bypassed the switch and connected the mains fuse. now the PT is doing what it should. i get ~500V on the main filter caps and the power tube plates. i get about ~-68V volts on the bias winding which drops to ~-42V through some resistors and stuff to power tubes' control grids.

the preamp tubes are lighting up BUT i cant seem to read any heater voltage, either on the preamp tubes or on the power amp tubes (those tubes are currently NOT in the amp, btw). why/how are preamp tubes lighting up w/o heater voltage? all of the heater pins are measuring ~5 ohms to ground....

thats where im at now - trying to track down the heater wiring.

now that ive sorted through some of the wiring, i see that there is a brown wire and an orange wire that go NOWHERE (dont worry just three pics!):

http://dropcanvas.com/#1529c4668Pi1J4

in the picture titled "my amp" you see two wires coming out of the secondary of the PT that go to nowhere nodes. i disconnected them, checked and the BROWN wire is 0 ohms to transformer casing/chassis ground. the orange wire shows high (~500K - 1M) resistance to the power taps on the primary side of the PT, but they are unstable, going up and down. might this orange wire be heater ground?

in the pictured titled "working amp" there is a brown wire coming from the secondary of the PT that goes to the cathode of the biasing diode. if that brown wire goes to ground/PT casing, why would it go to that side of the biasing diode? furthermore, where is the orange wire that i have in my amp?? its missing completely.

notice also that in the "working amp" there is an additional gray wire going from the secondary of the PT to a point on the chassis. im thinking this might be the heater ground? in my amp there is only one (brown) wire going to the chassis from the secondary of the PT.

in "my amp 2" you see there is a 56k resistor that goes from the cathode of the biasing diode to ground. that, of course, is nowhere to be found in the working amp. there is ~40V across this resistor.....there other end of this resistor, and thus also the biasing diode, is wired through a 47nF cap to the middle of the bridge. is this resistor stealing my heater voltage?

should i redo the wiring of my amp to match the working amp? if so, how can i figure out what the brown and orange wires coming from the secondary of my PT are? where is the heater ground?? are the two brown wires mixed up? if so, how can i tell/test them to see which is which? what's weird is the bias voltage is correct, indicating that that part of the amp is wired correctly....

(note that on Gonz' diagram the heater wires are red - mine are green. his HT taps are black and black, mine are black and red.)

coool - ill make one today.

is the diode section just for powering the fan? ooooo i see is it just stealing a bit of the load's AC, rectifying it, filtering it, and powering the fan?? so clever!

Quotea cobbled up bunch of power resistors, voltmeter and calculator to apply the Power Law works too.

as far as a dummy load goes:

can i just wire together a bunch of power resistors in parallel?? if i am just interested in power output.

say i wanted 100W @ 4 ohms, would 10 40 ohm/10W resistors do the trick? do i need to simulate inductance somehow? or is that not crucial to this application?

(and the reason i asked about DC volts across the load is cause you said voltmeter up there ^^.....)

Quoteilyaa!!!  What is the amp outputting to the speaker?  {musta bin a late night post I guess  :loco }

hehehe....yayaya i was just making sure!

i know: DC on the speak = death

check it out:

ran into someone with a perfect condition sound city concord combo!

he let me take some pix (i couldnt take it fully apart and kind of had to rush....) but heres what i got:

http://dropcanvas.com/#Mw8P8TI4N7mKe4

what i saw and gonz' picture dont quite jive....

it seems like the fat yellow wire going into the PT is the 115V tap (seeing as thats the way both my amp and the working one are wired). there are no orange wires going into the PT. the only orange wires are the ones around the mains fuse. also, doesnt it seem like the red wire is the bottom, rather than the top of the primaryy, seeing as its also connected to green/yellow (safety)?

in the absence of a working selector, how can i hard-wire it?

yeah i have a scope to put on there...

am i measuring DC volts with the meter? or p-p volts that the scope is showing? i assume the latter....

i guess my real question is:

is that stuff always bad? should it be cleaned off if its all over the solder joints?

so the procedure is:

plug in dummy load - turn on amp - feed signal (knobs all the way up? halfway up?) - measure voltage across dummy load?

QuoteDid you specifically resolder all the pins of all the power tube sockets?

i resoldered the phase inverter pins and i THINK i did the power tubes but i dont remember now. i will go over the whole tube board again, though, just in case!

and ill do those readings -

Roly:

Quotecould be the OP bottles getting tired, but I always test before replacement

what do you mean test? is there a way to tell the power tubes are bad other than with your ears? any actual, measurable indicators?