by the way.....did what you asked but no signal across r24 and r25....and they are 100k resistors allright.
P.s. I still think it is worth replacing the supertex part with the IXYS one.. if anything the board would be completely stock
P.s. I still think it is worth replacing the supertex part with the IXYS one.. if anything the board would be completely stock
OK, we are getting down to desperate measures here.
You can try removing or lifting one end of R30 and R31, and C17 and C18. This should leave only the plate load resistors connected to the 6CB6 plates.
This will shift the bias point a bit. With no AC signal, make sure the DC voltage on the 6CB6 plates is still reasonable (between 100V and 200V). Adjust the driver balance for 0V DC between the 6CB6 plates (TP9 and TP10).
Then apply the AC signal, and measure AC volts from TP9 to TP10.
If STILL nothing, the problem has got to be the 6CB6 tubes?
Any budding geniuses listening in with any other ideas?
Pete
You can try removing or lifting one end of R30 and R31, and C17 and C18. This should leave only the plate load resistors connected to the 6CB6 plates.
This will shift the bias point a bit. With no AC signal, make sure the DC voltage on the 6CB6 plates is still reasonable (between 100V and 200V). Adjust the driver balance for 0V DC between the 6CB6 plates (TP9 and TP10).
Then apply the AC signal, and measure AC volts from TP9 to TP10.
If STILL nothing, the problem has got to be the 6CB6 tubes?
Any budding geniuses listening in with any other ideas?
Pete
Another thing you can try... replace the CCS with a ~3.3k resistor. It should bias up in about the same place, and should work almost the same...
Right now if I start the amp the plate voltage is beyond "reasonable" hovering at 212v..
I will try this but is there absolutely no way the supertex chip is working differently from what whould be expected?
If I swap D and S basically associating them with cathode and anode I do get a negative voltage (tested) on the plate and I would guess a negative voltage on pin 2 and 7. This would rule out the pinout as the source of my problems but not the chip's response itself... ??
I will try this but is there absolutely no way the supertex chip is working differently from what whould be expected?
If I swap D and S basically associating them with cathode and anode I do get a negative voltage (tested) on the plate and I would guess a negative voltage on pin 2 and 7. This would rule out the pinout as the source of my problems but not the chip's response itself... ??
I have been far to busy at work to answer any posts or PM's during the week. Computer use is monitored at work and all my posts come from my smartphone during the day. It's very slow and clumsy with fat fingers. I get about 1 hour an evening for Tubelab stuff right now. I offer a few thoughts.
The Supertex and the IXYS parts have the same pinout. I have used both in my Tubelab amps with only a resistor change. Haven't tried a Supertex part in the red board.
I have been experimenting with guitars and amplifiers but I haven't tried connecting the guitar to the red board. Both of my red board amps are temporarilly stashed in the closet for a while. My wife has been home for only 9 days this year so the red board was connected in the living room with 600 volts exposed. She will return home shortly so a major clean up effort is underway. All stuff with low WAF is being put away.
There was a thread a couple of years ago where a builder had very low output on a Tubelab SSE board. Several hundred posts could not solve the issue, so I had him send me the board. Turned out that he had drilled out the holes in the PC board to accomodate the fat leads on Auricaps. This removed the through hole plating. All DC readings will check out good. Did you make any modifications to the PC board?
The Supertex and the IXYS parts have the same pinout. I have used both in my Tubelab amps with only a resistor change. Haven't tried a Supertex part in the red board.
I have been experimenting with guitars and amplifiers but I haven't tried connecting the guitar to the red board. Both of my red board amps are temporarilly stashed in the closet for a while. My wife has been home for only 9 days this year so the red board was connected in the living room with 600 volts exposed. She will return home shortly so a major clean up effort is underway. All stuff with low WAF is being put away.
There was a thread a couple of years ago where a builder had very low output on a Tubelab SSE board. Several hundred posts could not solve the issue, so I had him send me the board. Turned out that he had drilled out the holes in the PC board to accomodate the fat leads on Auricaps. This removed the through hole plating. All DC readings will check out good. Did you make any modifications to the PC board?
Tubelab.com To be sure I soldered all pins through (on both sides) to avoid just this kind of mistake....
However I treasure your experience and will check again!
However I treasure your experience and will check again!
If I made this silly mistake then I should buy a second board from pete and be extracareful with soldering (only backside soldering this time)..
Just install a 3.3k resistor between pins 2 and 3... so it connects between the resistor (R37, already in place on the PCB) to -60V and the tube's cathodes.
Pete
Just soldered everything back in place....nothing..
I guess Pete will have a paypal incoming email soon 🙂
I guess Pete will have a paypal incoming email soon 🙂
Could the problem partially be attributed to the low filament voltage?
+/- 10% is typically applicable and 5.3V is outside that range.
A follow up toThis Post. After taking a closer look at Q2, there is no doubt the part shorted out. The Fuji component I used isn't insluated like the recommended part and it seems that it was arc'ing over to the nut that attaches to the chassis which is grounded. I did see a few arcs to the chassis before it died and it gave up the ghost. It probably didn't help that I used a 120uF cap for C6.
So my plan now is to try something for fun. I'm going to lift R56 and D9 and drop a Triad C-14X just cause I have a few laying about. Hopefully nothing else got fried.
So my plan now is to try something for fun. I'm going to lift R56 and D9 and drop a Triad C-14X just cause I have a few laying about. Hopefully nothing else got fried.
Are the ipod output numbers measured while connected to the amp? mV numbers are very, very low. Is the (R64) input grid leak really 100k? A 100R for instance could kill the input voltage. That amp should have an input signal on the order of 0.1-1V or 100x what you've measured. The numbers "seem" wrong. An ipod with such low output wouldn't provide a big enough signal, even for earbuds. At least I don't think so. Try measuring across the actual input jacks for DCR and capacitance.
Not much I know, but didn't see where that aspect was checked.
Good luck,
Stuart
an ipod only does about 1vpp and 50mw. Its meant for 16ohm buds, the line out should be alot louder.
Right. He only measured 0.008V, which leads me to think something is loading the crap out of it.
Update - I sent Edcor an email with pics of the damaged end bells. 2 days later Fedex delivered a package with 2 end bell and 2 Edcor pens.
But that was measuring "music" with a DMM. Such a measurement is fairly meaningless since most DMMs cannot make an accurate measurement of AC above 100Hz. I think he got 0.1V RMS at 50Hz. This is one of those occasions where a scope would really help. 🙂
very true! However if there is such a principle...I would have seen an amplification of whatever "value" I saw on the input side...
I actually tried pures sinewaves with a tone generator...trying to tune the frequency with the DMM characteristics.. The board is not amplyfying...it is not a question of source. It is simply not doing anything 🙂
I actually tried pures sinewaves with a tone generator...trying to tune the frequency with the DMM characteristics.. The board is not amplyfying...it is not a question of source. It is simply not doing anything 🙂