21

501 Single Host / Re: Dead Transformer?

« Last post by JPK on June 03, 2025, 11:56:08 AM »

Were you able to solder the LM2586 heatsink tab to the PCB? This connection ensures good heat transfer from the case to the outside.
Check that the 2 regulators U1 & U2 are not touching any other pad or solder joint.
Can you check the switcher alone like in step 19 of the switcher assembly guide?
Is the LM2586 getting very hot?

22

MU524 Vari-Mu Tube Compressor / Re: MU524 Low Tube PCB Voltage

« Last post by JPK on June 03, 2025, 11:43:16 AM »

Can you measure the output noise voltage with the pots at max and the jumper removed?
This to make sure the noise doesn't come from the side chain.

23

MU524 Vari-Mu Tube Compressor / Re: test step 6 voltage

« Last post by JPK on June 03, 2025, 11:25:02 AM »

Je vous l'envoie.

24

MP573 Microphone preamplifier / Missing Capacitors

« Last post by musicarr on June 02, 2025, 04:48:15 PM »

Hi,

I'm in the middle of the build, and it looks like I'm short three (3) 330u-25v capacitors. There should have been 9, but there were only 6. I purchased two of the pre's and checked the second one, and there are 9 there, so that's good. But I'm short three (3) on the one I'm currently building. What's my best option here? Do you send me the 3 missing capacitors, or shall I just get them another source like amazon:

Replacement for 6 pcs Panasonic FM Series Capacitors 25V 330uf Low Impedance
https://www.amazon.com/pcs-Panasonic-FM-Capacitors-330uf/dp/B073YR6GCY/ref=sr_1_1_sspa?crid=2FZSVGKV9AHY6&dib=eyJ2IjoiMSJ9.lYGszSaGmIKqSmxQ-NYYR3toB8oaNxkK1x6ow_9wMxRNUkzN02RcFEcB3edtqYU9UtljTMxS0N6U717AmUy53o8btpqtdoBJVeTYAm_l0R3h-6-EotxYrAY9uudKCvvi8K02SvPwAy9CEQ-2dn7UUFWkgOnpxVdACeHKNRSpjB0XZWaVvJdwpTo5GnCYXifRGbXCMuf5gjOP7P07xCfgDqmMKBiYHhYITMEqpUO3dig.ODc-pEs8bNJvWepUptD3d3cL4qy-FmY6WLl7NM9Gcik&dib_tag=se&keywords=330uf+25v+capacitor&qid=1748875453&sprefix=capacitor+330uf%2Caps%2C181&sr=8-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1

If the latter, I just want to make sure I get the correct ones.

Thanks

25

501 Single Host / Dead Transformer?

« Last post by Lamu95 on June 01, 2025, 05:54:19 PM »

Hi,
I've completed the 501 and the MP 573 kit. I managed to get all the voltage checks right in both units but the transformer (T1) on the 501 switcher was buzzing. It was audible just by ear and also through the MP 573. After some inspection, where I couldn't find any mistakes in the circuit, I plugged in the 501 again but now the transformer seems to be completely dead. I've made continuity checks and everything seems to be fine before and after the transformer. Also I'm reading 11.5 V at the input of the transformer but no voltage coming out of it.

 

For the switcher I'm reading:
+11.5V at the +12V input pin
0V instead of -19V
2.24V instead of +19V
1V instead of +55V

Could it be that I killed the transformer when I made the solder connection on the copper tape by applying heat for too long?

26

MU524 Vari-Mu Tube Compressor / Re: MU524 Low Tube PCB Voltage

« Last post by seanlew98 on June 01, 2025, 02:07:21 PM »

Built my X-10 rack and tested, still the same noise, maybe down by .5dB at most so effectively no change. Also tested this with a RND chasis, same issue noise still very prominent. Is it possible it's the tube? Or any suspect within the other parts that may have caused this?

Thanks!

27

MU524 Vari-Mu Tube Compressor / Re: test step 6 voltage

« Last post by PMswing on June 01, 2025, 12:30:24 PM »

Ok, je n'ai pas de résistance de 3K3 pouvez vous m'en envoyer ou me conseiller où m'en procurer ?

Merci

28

MU524 Vari-Mu Tube Compressor / Re: test step 6 voltage

« Last post by JPK on June 01, 2025, 11:19:18 AM »

Donc vous avez pu tout régler comme c'est spécifié.

Je vous propose de réduire R34 de 4k7 à 3k3 par exemple pour augmenter la sensibilité du vu-mètre.

29

MU524 Vari-Mu Tube Compressor / Re: test step 6 voltage

« Last post by PMswing on June 01, 2025, 09:47:15 AM »

Est-ce que les autres étapes se sont bien passées, en particulier les étapes 9 et 10 ?
à l'étape 9 je n'ai pas eu à ajuster TR4 il était déjà à -2V et je n'ai pas eu non plus à ajuster le pot out car il était aussi déjà à +6V
à l'étape 10 je n'ai que très peu ajuster TR5 il était déjà à 2.8V (au lieu de 3V demandé)

30

MU524 Vari-Mu Tube Compressor / Re: test step 6 voltage

« Last post by JPK on May 31, 2025, 11:06:38 AM »

en tournant TR6 à fond je monte seulement à 4dB au lieu des 6db demandés sur le vu mètre
Est-ce que les autres étapes se sont bien passées, en particulier les étapes 9 et 10 ?
Si c'est bien le cas, il faudrait juste réduire R34 de 4k7 à 3k3 par exemple pour augmenter la sensibilité du vu-mètre.