shouldn't as the behaviour starts with initial power up and when toasty, they are well within their operating specs.
I disassembled the amp last night but have not captured any of the critical measurements yet - my day job has been a little demanding lately
..dB
I disassembled the amp last night but have not captured any of the critical measurements yet - my day job has been a little demanding lately
..dB
Indra the Genius
Voltage between pins 3 & 4 is 0.22V
to ground: pin 3 = -4.17 , pin 4 = -3.94 ~ 0.22 as measured directly.
I did a little digging in the box of parts and have everything needed for the patch - IRF520,resistors and 24V zener. This will be my short term fix and then I will consider options.
The other measurements had me questioning my sanity
Line AC 118.5 V
Secondary : Unloaded - 19.8VAC , Loaded 19.2 VAC
Rectified : Unloaded - 26VDC , Loaded 23.4 DC ( more aligned with the expected 10% drop )
this is using the same DMM as I had previously used which gave me the 25.4 VDC loaded.
not able to get a measurement across the gate resistor?? = possibly 0.1mV
I am really pleased that I at least understand the 'why' for my amps behaviour.
Thanks to ZM and Indra for not giving up
..dB
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You are welcome. However, a 24v zener will not regulate if your rail is 23.4V. Replace the zener with a small capacitor 10 - 100uf instead for a cap multiplier as a quick fix. Consider using 22V zener and an npn darlington later.
Have fun.
Have fun.
that's showing that data for SIT Ugs isn't what you're writing all the time!!
meaning - your set of SITs isn't adequate for SissySIT
there is simply no big enough voltage window for opto bjt to be squeezed in
- now - you can try pure DEFiSIT - just short pins 3 and 4 of opto and set DC offset on out
meaning - your set of SITs isn't adequate for SissySIT
there is simply no big enough voltage window for opto bjt to be squeezed in
- now - you can try pure DEFiSIT - just short pins 3 and 4 of opto and set DC offset on out
that's showing that data for SIT Ugs isn't what you're writing all the time!!
meaning - your set of SITs isn't adequate for SissySIT
there is simply no big enough voltage window for opto bjt to be squeezed in
It is bizzarre as I measured (more than once) Ugs at 19V to be 3.7
(because high mu, it is probably very different at 24v)
I am more pleased to know that it isn't something I did while building.
I can now sit back and enjoy knowing that nothing is likely to blow up
.. dB
try shorting optopins , as I wrote
also - you din't confirmed measurements of Donut secondaries , we still don't know real reason why you are having so high rails
I can bet that AC is in range od 20V, not 18
btw- there is a reason why I declared 24Vdc for SIT testing , in procedure explained in SissySIT thread
maybe you mentioned using 19V , in that case I simply overlooked
aha - is it still sounding good?
also - you din't confirmed measurements of Donut secondaries , we still don't know real reason why you are having so high rails
I can bet that AC is in range od 20V, not 18
btw- there is a reason why I declared 24Vdc for SIT testing , in procedure explained in SissySIT thread
maybe you mentioned using 19V , in that case I simply overlooked
aha - is it still sounding good?
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Nope, yours are not likely to be high mu. It is normal SIT charactristic to have different Vgs for a certain Iq when measured at a different Vds. It is important to note that your pair of THS have the most desirable characteristics, the Vgs is good for the original DEFiSIT as Papa designed. Try the amp as ZM suggested and monitor Iq closely.
yes - you are once again correct
it was before I pulled it apart to get the measurements.
I will convert to DEFiSIT
..dB
so , Silly ZM - blame on me , completelly
😛
... same as I'm always blaming Pa ...... exactly right person for that
Jumpers across opto , rail voltages unchanged. Settles to zero pretty quickly with little change over a few hours and current at around 2.5A burning
new (inaccurate) artwork
sounding just as glorious as before
..dB
new (inaccurate) artwork
sounding just as glorious as before
..dB
it's worth examining - can you unwind some of your Donuts , it would be easier than shaving few volts of rails in any other way