bryce Goggin
New Member
I can get my measurements without killing the tubes. The voltage across the 4.7K cathode resistors is 35.6 (for v3a) and 34.9 (for v3b).
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I can get my measurements without killing the tubes. The voltage across the 4.7K cathode resistors is 35.6 (for v3a) and 34.9 (for v3b).
email the manufacturer about the high voltage problem and ask for the design plate or cathode current in the final stage. It would be extremely helpful to request the design current loading figure on the +270V line and +240V line to aid troubleshooting.
Hi Bryce,
This leads us back to the power supply section where you have replaced the components trying to located the fault. If you have not throw away the replaced power resistors, it is best to measure their resistance again, especially the three 470Ω resistors to confirm that they are really 470Ω. You should measure the voltage of TP1 which is also the DC tube filament voltage as requested by Eric in previous post.
At this moment in time, I think the best way forward is to email the manufacturer about the high voltage problem and ask for the design plate or cathode current in the final stage. It would be extremely helpful to request the design current loading figure on the +270V line and +240V line to aid troubleshooting.
The voltage tp1 is 11.3V. I will investigate the condition of the capacitors in this section of the supply. If these prove to be fine, should I then look to tweaking the value of R216?
I will also try contacting the fine people at LYNDCRAFT to see if they can shed some light on the plate current question.
Perhaps a discrepancy of .7 volts be the source of this problem?
Unlikely.
You should hold off tweaking the +12V supply until the fault on the +270V side is cleared. By then you can change the value of R217 9K09 to 9K6 and raise the voltage to +12V.
I can't find R217 or the TP; can you post the schematic section that you are looking at?
Thanks.
BTW the heaters are rated at 12.6V
Yeah, the schematic pin numbers should have told me that they're applying 12v to a 12v heater, just like they should.
For some reason I can't comprehend that this tube is a dual triode, even with the data sheet.
Has all of the revelant schematic been posted? I get lost without a road map [and sometimes, with].
What is this circuit chunk fed by? What is it feeding? 4700 uF at a delta V of 10 v is ~6 A.
hi,
Bryce has posted two dwgs , one of the psu and the other ECC83/82 section.
Do you want a ECC82/83 datasheet.?
I count two power supply schematics and the one tube wiring schematic in this thread. There also seems to be a lot of circuitry not shown (e.g., "PL 1") that the tube schematic shows as gozintas and gozoutas.
Probably I only need ECC82 and 81 datasheets if they are the ones that are dying, but the What the Heck, post it! Then we can reverse engineer the entire tube schematic.
From their resistor wattage values the 82s and 81s don't seem to draw much current and this does seem to be a current problem.
If we can figure out the Thevenin equiv. power supply resistance looking back into the supply then from the full load/no load voltage difference we can figure out exactly how much current is/is not being drawn.
I think now it was the Royal Lion Pub, near Portsmouth.
Fixing this or not, we are definitely having fun now!
I think now it was the Royal Lion Pub, near Portsmouth.
UK.hi,
Ref the valve or should it be tube data.
UK or USA.?
UK.
Can't open your link (computer problems).
Need tube data and graphs like for the 12AU7.
Are you aware this is a stereo unit? This should double the current draw.For the power supply,
Voc = 370 V
Rthev = 3 x 470 = 1400
So we need to draw 70 mA in order to get down to 270 V.
We got 330 V which means we were somehow drawing 370-330/1400 = only ~30 mA.
V3A & B probably are supposed to draw ~10 mA min. each, 20 mA min. total, from the graphical data and typical values I have from the Internet.
I should not have thrown out my RCA tube manual.
V2A & B cannot draw more than 240 V/200 K/2 = ~ 3 mA total no matter what both sections of the tube is doing. I don't have data for this tube.
For V1A & B I don't know what value R3 & R4 have but if you divide 110 by half of R3 + R4 you can figure how much max current this stage must draw.
It looks like 3 mA per section is the typical value with this tube from what data I could find on the Internet.
So we're up to ~30 mA for this amplifier.
Where does the +110 V that feeds V1 come from?
Are you aware this is a stereo unit? This should double the current draw.
As far as the 110 V goes. This is on the supply drawing.