Sorry, man! I know it stinks to make another trip, but you must have an incandescent bulb. That's why it works - if the device draws to much current - then the filament takes the brunt and glows. Halogens don't do that.
🙁
Hope you get it going. You can still build it up and maybe find a bulb or two around.
Edited to add - strongly recommend reading the article I linked and/or watching a YouTube video or two. It'll help.
The good news is that your MOSFETs likely aren't bad per your previous posts. You're not releasing the magic smoke on anything are you? Still don't remember what current symptoms are.
🙁
Hope you get it going. You can still build it up and maybe find a bulb or two around.
Edited to add - strongly recommend reading the article I linked and/or watching a YouTube video or two. It'll help.
The good news is that your MOSFETs likely aren't bad per your previous posts. You're not releasing the magic smoke on anything are you? Still don't remember what current symptoms are.
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Thanks ItsAllInMyHead. The only true incandescent bulbs I found were 150w and 300w. I think I have a couple of 40w bulbs laying around.
I did read the article. I figured since halogens still use a tungsten filament, it would work.
Symptoms: R7 is super-sensitive around 0 volts offset. The voltage will swing wildly, + or -, with the slights turn. The offset will also not stay constant. When I pull the jumper off the input when the offset is 0 volts, it will shoot up (I think positive) 10-40V.
I did read the article. I figured since halogens still use a tungsten filament, it would work.
Symptoms: R7 is super-sensitive around 0 volts offset. The voltage will swing wildly, + or -, with the slights turn. The offset will also not stay constant. When I pull the jumper off the input when the offset is 0 volts, it will shoot up (I think positive) 10-40V.
ZM: I'll check right now. BTW: I measured the last set of MOSFETs I pulled:
4.13
4.14
4.09
4.15
They're all good (assuming I'm measuring correctly). That got me to thinking: Is there a combination of settings achievable with R27 and R7 that would show a bias in the desired range, but be way off for the correct settings?
I'll get that measurement straight away.
4.13
4.14
4.09
4.15
They're all good (assuming I'm measuring correctly). That got me to thinking: Is there a combination of settings achievable with R27 and R7 that would show a bias in the desired range, but be way off for the correct settings?
I'll get that measurement straight away.
OK, that's good
we expect there approx. zener voltage (9V1) minus one Vbe voltage (0V65, of Q2)
that divided with 1K gives current through LTP , so somewhat above 8mA
now, one DVM across outputs, second DVM across any of big 3W source resistors
how close you can go to desired values , of (say ) 400mV across source resistor and as close to 0 at output ?
remember that you need to fiddle with trimpots iteratively, in half steps
we expect there approx. zener voltage (9V1) minus one Vbe voltage (0V65, of Q2)
that divided with 1K gives current through LTP , so somewhat above 8mA
now, one DVM across outputs, second DVM across any of big 3W source resistors
how close you can go to desired values , of (say ) 400mV across source resistor and as close to 0 at output ?
remember that you need to fiddle with trimpots iteratively, in half steps
I can always get the desired voltage across the source resistor - and it's pretty consistent.
The offset at the output is unstable. I can never get it within a volt from 0 for more than a couple seconds.
One thing I noticed... When I'm adjusting R7, the changes to the output offset are pretty steady until I get close (within 2/10 of a volt) to what I'm measuring across R8.
Is that significant?
The offset at the output is unstable. I can never get it within a volt from 0 for more than a couple seconds.
One thing I noticed... When I'm adjusting R7, the changes to the output offset are pretty steady until I get close (within 2/10 of a volt) to what I'm measuring across R8.
Is that significant?
you're inventing correlation there, which doesn't exist
R8 readout is important to confirm that Q2 CCS is functional , nothing else and exactly that
OK, let's assume that you have oscillation there , for Gremlins sake
do you have few 1nF caps around , even lowest voltage will do ?
R8 readout is important to confirm that Q2 CCS is functional , nothing else and exactly that
OK, let's assume that you have oscillation there , for Gremlins sake
do you have few 1nF caps around , even lowest voltage will do ?
The closest thing I found were .1mfd coupling caps. I don't mind ordering if you care to specify exactly what you'd like me to use, though.
two positions, 1nF/63V will do, shown on attached pdf
buy anything with leads.... really anything will so , I mean - any type of solid cap
in case of your amp, you'll need to be inventive and solder one between B and C of Q4 (Aleph CCS bjt) and between Q3 C and speaker's output route
if desperately needed, I can edit your ref. schm to include these
while you're waiting to get them, either from Mouser, or nearest Tobacco Store, play a little game - look at functional channel and bad one, and try to visually check - is there any difference you can find
buy anything with leads.... really anything will so , I mean - any type of solid cap
in case of your amp, you'll need to be inventive and solder one between B and C of Q4 (Aleph CCS bjt) and between Q3 C and speaker's output route
if desperately needed, I can edit your ref. schm to include these
while you're waiting to get them, either from Mouser, or nearest Tobacco Store, play a little game - look at functional channel and bad one, and try to visually check - is there any difference you can find
Just in case Zen Mod, are you aware you posted Aleph 30 schematic. I know they are related but just in case. Don’t want to confuse the OP.
just in case, you read that I transferred caps in question to parts nomenclature used in ref. schematic?
this file , made by Algar_emi, helped numerous times in troubleshooting Alephs
🙂
this file , made by Algar_emi, helped numerous times in troubleshooting Alephs
🙂
Zen Mod: Thanks for the description! I think I can proceed without a modified schematic.
I found another way to bide my time... Since the Jensen transformers came in today, I built the F6. Rushing to hear what it sounds like, I replaced the broken channel with one of the F6 boards: Frankenamp.
It took some fiddling to get the bias on the F6 spot-on; but I've been listening to the combo for about an hour now. So far, the F6 has less gain, less texture, and less depth to my ears. I adjusted the balance to accommodate for the gain. I'm happy I'm hearing something in stereo, though 🙂
More than ever, I'm looking forward to getting the Aleph J working!
I found another way to bide my time... Since the Jensen transformers came in today, I built the F6. Rushing to hear what it sounds like, I replaced the broken channel with one of the F6 boards: Frankenamp.
It took some fiddling to get the bias on the F6 spot-on; but I've been listening to the combo for about an hour now. So far, the F6 has less gain, less texture, and less depth to my ears. I adjusted the balance to accommodate for the gain. I'm happy I'm hearing something in stereo, though 🙂
More than ever, I'm looking forward to getting the Aleph J working!
A halogen will work just fine. A kind person pointed out to me that a halogen bulb is a type of incandescent bulb. I had florescent on my brain. You had it correct in your follow-up post. 😀 Sorry for my goof! Looks like you're making progress.
Love the "Frankenamp" 😀
I have some great news! I got the new matched pair of JFETs in the mail today. Immediately following work, I installed them. Bias and offset now function properly! I'm about to connect my speakers and break this baby in!
I have to assume I measured the old ones improperly. I have them off on the side, and want to run additional tests on them to learn from.
Thanks to all for your help!!!
I have to assume I measured the old ones improperly. I have them off on the side, and want to run additional tests on them to learn from.
Thanks to all for your help!!!
