Done, fully recapped. R41 and Rbonus were replaced with 8k resistors, all I had underhand was 8 or 20k...Recap it and get it over with especially C16
V = 0VMeasure V across R38 in the OFF position.
V = 0V, in both ON and OFF positions. interestingly, the LED did not turn green when switched to ON, with C16 shorted...With no signal. Short C16 and measure V across R41
Hard to estimate, I'd say 0.5-1 sec.Check delay to LED change from OFF to ON.
I'd say a good couple of seconds here, longer than OFF-ON change.Move switch to AUTO.
Apply music. Check delay to LED change.
I'm just confused as to why ON wouldn't show a green LED with C16 shorted?! Expected?R43 and the internal leakage current of C16 allows the timing circuit to discharge when the mains are cut. At 5RC, the cap is about 99% discharged. I can fix that with a J174 FET and a resistor. The resistor across the cut must be used too.
I'm off to Paris on sat, south of france on wednesday, spain on Friday.... Then I have a few days of work, and I'm off to Italy for a few days... Next few weeks will be a bit more on and off so I'm trying to speed things up, or at least stop somewhere reasonable! Can't complain about holidays though...That ought to keep you busy for a while.
Recap it and get it over with especially C16
Done, fully recapped. R41 and Rbonus were replaced with 8k resistors, all I had underhand was 8 or 20k...
Perfect
Measure V across R38 in the OFF position.
V = 0V
Good. Hopefully you switched to the Millivolt scale
With no signal. Short C16 and measure V across R41
V = 0V, in both ON and OFF positions. interestingly, the LED did not turn green when switched to ON, with C16 shorted...
Can't. Only happens when C16 gets charged above D5's voltage
Check delay to LED change from OFF to ON.
Hard to estimate, I'd say 0.5-1 sec.
Better number - don't you think?
Move switch to AUTO.
Apply music. Check delay to LED change.
I'd say a good couple of seconds here, longer than OFF-ON change.
Lot's of reasons for a slight change. I thnk it's a better delay than stock?
R43 and the internal leakage current of C16 allows the timing circuit to discharge when the mains are cut. At 5RC, the cap is about 99% discharged. I can fix that with a J174 FET and a resistor. The resistor across the cut must be used too.
I'm just confused as to why ON wouldn't show a green LED with C16 shorted?! Expected?
Totally. If C16 can't charge, then delay will be infinate.
That ought to keep you busy for a while.
I'm off to Paris on sat, south of france on wednesday, spain on Friday.... Then I have a few days of work, and I'm off to Italy for a few days... Next few weeks will be a bit more on and off so I'm trying to speed things up, or at least stop somewhere reasonable! Can't complain about holidays though...
Luck you. Hiding from the big wedding?
Would you happen to have another amp lying around? If you did then I would input a signal on Low level in or Speaker in and see if there is hum present on Line out.
Check for the presence of any AC between SG of the connector and ground (No signal applied). If you have a frequency counter mode, check for the abcense of 2x the main frequency.
Let's do something a little bit different than before.
Remove Q8, Q9, Q10 and Q11
Put a 1K or so resistor between where E and C go on Q8 and Q9. Estimate the current as 80/((2 * R)+220) to size the resistors.
Tell me what you currently have installed for R13 and R14
Look at voltage between EC of Q7
Look at voltage between junction of R15/R11 and base of Q7
Look at voltage between junction of R16/R12 and the base of Q7
Consider installing the bias pot modification.
Remember as R14 gets bigger the higher voltage is applied between the B and E of Q7. The resistance should be highest in the CW position of the bias potentiometer.
Yep - but an amp specifically, and not simple an mp3 player or something else like that? Should be the same for testing?Would you happen to have another amp lying around? If you did then I would input a signal on Low level in or Speaker in and see if there is hum present on Line out.
0.003V ACCheck for the presence of any AC between SG of the connector and ground (No signal applied)
DMM has a "Frequency measurements" mode, I assume that's what I'm after? If so, nothing is showing.If you have a frequency counter mode, check for the abcense of 2x the main frequency.
R13 = 3.3k (unchanged)Tell me what you currently have installed for R13 and R14
Yep, would be a good idea, back with a 3.3k resistor (so 3.3 + .5, potentially). This time I'll glue gun the ends so that I don't short anything with the extra PCB.Consider installing the bias pot modification.
Let me roam through my growing draw of electronic components, see if I have a 1k resistor underhand. R being Resistance? If so, current will be around 0.036A, so that means with a 1/4 W resistor I shouldn't exceed 7V. Should be ample, I recall Q7 being around 2.5V roughly.Put a 1K or so resistor between where E and C go on Q8 and Q9. Estimate the current as 80/((2 * R)+220) to size the resistors.
I'll go and pick up a couple of 2W 1K resistors this afternoon, 1/4W would have been a little flimsy if the voltages are anywhere close to those of Q10-Q11...(0.036^2) * 1K, so a 2W resistor will be fine.
Thanks. Will take your word for that. I'll isolate using electrical tape, and once everything is setup permanently, I can glue the PCB add-on properly with an epoxy; will be cleaner.Warning, the glue gun may not be a good fastening method. Been there. Done that.
Done. Q10-11 still out of course.Put a 1K or so resistor between where E and C go on Q8 and Q9.
Look at voltage between EC of Q7
Look at voltage between junction of R15/R11 and base of Q7
Look at voltage between junction of R16/R12 and the base of Q7
the Q8/Q9 E-C resistor does absolutely nothing except get hot
More seriously, not sure I follow here...+V to 1K to 220 to 1K to -V. Oops!.
OK, so something like 3k + 0.5k pot, and then we can fine tune.Get the R14 combination going and set to 3.3K or less
You bet; will be keeping an eye on that one for sure!Monitor voltage across Q7 E-C. Don't let it get above 2.4V
Sounds good to me; this could be mean either increasing, or decreasing R14 resistance? Or will it necessarily go one way or the other?Reduce Q7 E-C to the minimum value you can get
More seriously, not sure I follow here...
OK, so something like 3k + 0.5k pot, and then we can fine tune.
You bet; will be keeping an eye on that one for sure!
Sounds good to me; this could be mean either increasing, or decreasing R14 resistance? Or will it necessarily go one way or the other?
Got through a few too many Q10 and Q11 so far!
Go for broke. Leave out Q10 and Q11 and use the 25 W lamp.
Get the R14 combination going and set to 3.3K or less. Monitor voltage across Q7 E-C. Don't let it get above 2.4V
Welcome back. Yep. go for broke. The moment you see decent adjustability, back it off. Put the heatsinks back. Do a brief sound test and final adjustments.
You could. but be VERY careful make some small heatsinks out of a cooking aluminum throughoway container or multiple folds of aluminum foil. Clip it into place with a clothespin. Watch for shorts.
You need to adjust it while monitoring E-C. My guess is it will "suddenly" start to work while turning it.
Voltages across R4 and R9?
and
Voltages across R11 and R12?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?