Thankyou for this reply!
Could anyone reading this thread plug their laptop headphone output to their amp and max everything out?
Can you drive the amp into clipping?
Thanks
Alex
My laptop puts out 0.6V RMS (just measured with sine wave playing) - that should normally be sufficient to drive an integrated amp to full power when cranked all the way up (it does drive my 1.5W SE and 10W PP amps)
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an integrated amp usually contains a pre amp module... or do you mean something else? with a preamp the input sensitivity is lowered as one would expect, correct?
I don't recall the details but would expect Pete's red board to have input sensitivity in the 0.5-1V range with most small signal tubes that it can accommodate so laptop soundcard output should drive it pretty loud. Even iPod or some other portable player should have a sufficient signal level for serious in-room levels.
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I received the Edcor OPT's today. Is it common for the end bells to be dented? I know it is just superficial but I wanted to know if I should ask for replacement end bells.
I've received a few of their bigger OTs with dented end bells. Their packaging just isn't up to the abuse from UPS. I did manage to haggle some replacement end bells from them. I got the impression they didn't think it was their fault. (but filing for damages thru UPS and all that would be a major pain I think.) One OT even got one of its lead wires cut short by shearing against a mounting tab. Fixed that one myself. I tried hammering out the dent from one OT, but it looks poor. Maybe if one had the proper rubber mallets and tools.
Mine are the 3.3K 100 Watt versions and one of the dents is at the top back corner, about the size of a penny cut in half and fairly deep. It looks kind of creased so I don't think I can hammer it out. Maybe I could Bondo and repaint. The other OPT has a larger, but more shallow dent also in the back. I may just take a picture and send it to Edcor and see what they say. The OPT's arrived earlier than estimated and I haven't soldered the components in the board yet so if I leave it alone over the weekend I may decide that it adds character.
I'm not sure what's going on at Edcor, but I ordered (6) 5K, 100W OTs and they were shipped two per box. The way they were packed there is no way they could have been damaged in shipment short of being smashed with something VERY heavy. They arrived in perfect condition. I think I would bring up the issue with Edcor before going to the shipper for damages.
The dented ones I got were generally packed in more than 2 to a box. The double or single boxed ones looked better packed. For a lead wire to get sheared off by a mounting tab though, it had to be one heck of a drop.
They do sell blank end bells if by any chance you wanted to change the color anyway.
They do sell blank end bells if by any chance you wanted to change the color anyway.
Each OT was in its own box wrapped in bubble wrap. Both boxes were packed together in a larger box with bubble wrap. All of the boxes look undamaged so I wouldn't think that it happened during shipping. I'll contact Edcor and see what they can do. In the worst case scenario I'll order new end bells and repaint.
I tried to input a 1khz sine wave from a tone generator (PC) and along the speaker cables I get 0v AC.
Music plays no amplification whatsoever.
Basically I have an amplifier that does not amplify.
If any kind soul can help me...maybe ask for measurements ecc I will be very grateful.
🙁
Music plays no amplification whatsoever.
Basically I have an amplifier that does not amplify.
If any kind soul can help me...maybe ask for measurements ecc I will be very grateful.
🙁
I will assume you've checked every DC voltage that's shown on the schematic, and they are all reasonably close (+/-20%) of what the schematic shows. If not, that's step 1.
You need to systematically debug the signal path - trace the signal through the amplifier. This would be easier if you used an oscilloscope, but you might succeed using only a meter.
By the way, many inexpensive DMMs will not read anything useful at 1kHz as they are designed for 50/60Hz use. You might need to use 100Hz... And many cheap DMMs will also read DC voltage on an AC scale, so if there is a DC voltage present it will give you an incorrect measurement. You can get around this by putting a capacitor in series with the DMM (like 1uF).
First, verify with the meter that you have an AC signal coming out of your source, and the meter can actually read the signal. Let's say it is 500mV RMS.
Next, check the voltage at pin 1 of VT8 to ground. It should be same as your source (500mV). If not, the problem is in the wiring between the input and VT8.
Check pin 1 of VT5 to ground. There should be no AC signal there.
Next, measure the AC voltage across R24, and R25. It should be much greater - depending on the input signal level, probably 5 or 10V RMS. It should be the same on each.
You can also measure grid-to-grid between pin 11 of VT1 and pin 11 of VT2 (for 6JN6 tubes) or pin 5 (for 6JM6 tubes), and you should get twice what you measure on the resistors.
If not, the problem lies in the driver stage. If the voltage is OK there, the problem lies in the output stage or OPTs.
You can try measuring the AC voltage from the output tube plates to ground (it should be much bigger yet), but you need to be careful, as there is a 325V+ DC voltage here. Your meter may not be able to measure this (see above). Again, you can measure plate-to-plate voltage as well (between pin 7s for 6JN6, or between the plate caps for 6JM6).
Also...
Make sure you have R3/R6 (for 6JN6) or R16/R20 (for others like 6JM6) installed correctly for the type of tube you are using. Only one or the other should be installed.
Make sure the tubes are really what they are supposed to be (e.g., 6CB6 not 6BC6)
Make sure the polarity of the input wiring is correct.
If using non-plate-cap tubes (like 6JN6) make sure the jumper under the tube sockets is installed (or not if using plate cap tubes).
Pete
One of the ones I recently ordered was dented as well. A soft dent, but alas. I sound be able to push it out.
Thank you Pete!
I checked everything out and it would seem that if I feed a 50hz tone I get a 0.1v AC signal. Clearly visibile in the DMM. If I play an mp3 I get something like 0.2/0.3v AC.
anyways I checked the voltaged on the pins of the 6cb6 tubes and they check out.
However across R24/25 I measure nothing or sometimes 0.1v AC
Nowhere near a multiple of a 100 of what I have as a signal.
Alex
I checked everything out and it would seem that if I feed a 50hz tone I get a 0.1v AC signal. Clearly visibile in the DMM. If I play an mp3 I get something like 0.2/0.3v AC.
anyways I checked the voltaged on the pins of the 6cb6 tubes and they check out.
However across R24/25 I measure nothing or sometimes 0.1v AC
Nowhere near a multiple of a 100 of what I have as a signal.
Alex
OK... so verify (with no input signal) that the DC voltage on both of the 6CB6 tubes is:
Pin 1 - 0V
Pin 2 and pin 7 - something around -2V (not sure of exact voltage)
Pin 5 - 130V +/- 30V
Pin 6 - 150V +/- 10V
...and also 6.3V AC between 3 and 4.
Are you using NFB? If so, remove R71 to eliminate it (just in case...)
Pete
Next thing to try: Pull the output tubes. Verify that R25 and R24 are really 100k (not 100 ohms or something else). Apply the AC signal to the input. Verify that you measure the input AC voltage between pin 1 of VT5 and pin 1 of VT6. Then check the AC voltage again on R24 & R25.
If still no signal, about the only thing it can be is the 6CB6 tubes.
Pete
and my findings are:
1. pin 1 - 0v on all tubes
2. pin 2 and pin7 - 2/3v max
3. pin 3-4 5.3vac
4. pin 5 - 187/188v
5. pin6 - 147/148v
All tubes show similar results.
No NFB applied and R71 eliminated
1. pin 1 - 0v on all tubes
2. pin 2 and pin7 - 2/3v max
3. pin 3-4 5.3vac
4. pin 5 - 187/188v
5. pin6 - 147/148v
All tubes show similar results.
No NFB applied and R71 eliminated
Yep positive....
This would suggest that the IXYS pinout differs from the supertex pinout...right?
it would seem that the only thing is either to expriment with the supertex part or simply ask you for a couple of chips 🙂
Anyways thanks a lot. You have been very kind and helpful. The forum is lucky to have you as an active member.
This would suggest that the IXYS pinout differs from the supertex pinout...right?
it would seem that the only thing is either to expriment with the supertex part or simply ask you for a couple of chips 🙂
Anyways thanks a lot. You have been very kind and helpful. The forum is lucky to have you as an active member.