"WHAMMY" Pass DIY headphone amp guide

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#463
mod_sonic said:
While working on my Whammy I shorted something(s). I thought I had blown the regulators and the LEDs were off. I have replaced the regulators but the LEDs are still not on, and I am getting 30V on the regulator outputs and the opamp power pins. Can anyone point me to the best places to troubleshoot the problem ?
Click to expand...

Sounds like open leds. The regulators have no ground reference. Zen Mods advice is good.
 
#466
Help !

wayne said:
Sounds like open leds. The regulators have no ground reference. Zen Mods advice is good.
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Wayne, 6L6 and Zen Mod,

Thanks for the advice. I will order more diodes and change them out. Bizarrely with the 833 opamp and 30V it plays and sounds fine ! Not sure how long that would last though before it started smoking so it's out of use for now. Back to my £13 JLH 1969 🙂.

I have photos I can upload if anyone thinks it would add anything, but replacing all the diodes first makes sense.
 
#467
Which LED ?

mod_sonic said:
Wayne, 6L6 and Zen Mod,

Thanks for the advice. I will order more diodes and change them out. Bizarrely with the 833 opamp and 30V it plays and sounds fine ! Not sure how long that would last though before it started smoking so it's out of use for now. Back to my £13 JLH 1969 🙂.

I have photos I can upload if anyone thinks it would add anything, but replacing all the diodes first makes sense.
Click to expand...

All,

I bought the Kingbright WP710A10LID LEDs in the BOM from Mouser with all the other bits. I can't order exact replacements because the postage will be ridiculous for such a small order. RS has lots of red Kingbright 3mm LEDs. What spec am I looking for please ? Forward voltage ? Reverse voltage ?
 
#469
mod_sonic said:
All,

I bought the Kingbright WP710A10LID LEDs in the BOM from Mouser with all the other bits. I can't order exact replacements because the postage will be ridiculous for such a small order. RS has lots of red Kingbright 3mm LEDs. What spec am I looking for please ? Forward voltage ? Reverse voltage ?
Click to expand...

I have a some spare LEDs drop me a pm with your address and I will put them in the post for you Monday morning.
 
#470
mod_sonic said:
All,

I bought the Kingbright WP710A10LID LEDs in the BOM from Mouser with all the other bits. I can't order exact replacements because the postage will be ridiculous for such a small order. RS has lots of red Kingbright 3mm LEDs. What spec am I looking for please ? Forward voltage ? Reverse voltage ?
Click to expand...

just pull them from anything broken you have in drawers

or use green ones , if you have them new

if you change color (thus voltage across ) , change in both rails
 
#472
mercedese63 said:
What exactly is the purpose of R39/R40? The schematic shows that they along with the volume pot forming some type of voltage divider influencing the gain in some way.
In a early post I read where Jim stated that they "have all to do with oscillations" or something along those lines.
I just don't understand why they're needed.

Thanks.
Click to expand...

Nobody can answer my question above about R39/R40??
 
#473
LEDs & Diodes

JamieMcC said:
I have a some spare LEDs drop me a pm with your address and I will put them in the post for you Monday morning.
Click to expand...

JamieMcC

That's very kind of you, but I have already ordered some from RS with the diodes. Fortunately they don't have minimum order values anymore and reliably deliver next day - so the bits should be here on Monday.

I took the diodes out of the board ready for the new ones and tested them with my multimeter's diode testing function. I got 585 with red lead to the anode and infinite resistance with black lead to the anode, which I think means they are OK - so it looks like the LEDs have blown. Nevertheless I will replace them all as advised and see what happens.
 
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