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Chip Amps Amplifiers based on integrated circuits

Newbee build: PA03 amp (LM4780)
Newbee build: PA03 amp (LM4780)
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Old 9th December 2016, 09:19 PM   #281
peranders is offline peranders  Sweden
Electrons are yellow and more is better!
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Join Date: Apr 2002
Location: Göteborg, Sweden
Newbee build: PA03 amp (LM4780)
If you can fit silver mica caps you can use those but why? NP0 is probably better for this application.
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/Per-Anders (my first name) or P-A as my friends call me.
SSR03 group buy. Sign up for interest HERE. 15 pcb's in order. 0 paid.
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Old 15th May 2018, 08:09 PM   #282
Sneeze is offline Sneeze
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Hey,

First of all: I'm not sure if it's OK to post my question in a thread this old. If not, please let me know and I'll start a separate thread for my question.

About two years ago I bought two Pavel Dudek PA03 PCB's in Peranders group buy. Now, after a closely reading the instructions on sjostromaudio.com and the hints in this thread I finally started on building my first amp!

I think I've soldered everything together correctly, but when I plug in the power I get no sound! As advised I build the dim bulb tester. When I use it the bulb flashes for a moment, and then dims down when relais click. Both relais work (I can feel them when I put my finger on them). I've bypassed the mute relais with a jumper. Voltages on the rails and test points seem to check out. I've also checked the zeners, they both work as expected. Because I didn't know what else to check, I've just replaced the amplifier chip, but still no sound.

Right now I'm not sure how I can further troubleshoot the amp, I'm only a beginner in DIY audio..

Is there anything else I can check? Or does anybody know what could be wrong?


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Thanks!
Christian
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Old 19th May 2018, 06:48 PM   #283
clog is offline clog  Netherlands
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Could it be that the amp is still in mute condition ? In my amp I omitted RE1 and jumpered JP4. Besides I see a lot of what seems to be metal particles between the fins of your heat sink. Better to be careful and clean the board thoroughly.
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Old 19th May 2018, 09:32 PM   #284
loafimus is offline loafimus  United States
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Newbee build: PA03 amp (LM4780)
Clog is probably spot on. From the manual:

Using the mute function the PA03 module can be switched to a low power consumption mode, normally called as "Stand by". You do not have to switch the main switch off. A wide range of applications can be found, for example in subwoofer amplifiers or active boxes. The mute function can be activated by the relay RE 1. If the mute pin on the input connector is connected to the earth (through a mechanical contact or PNP transistor). In case you do not use this function, the relay RE 1 need not be mounted, you must use the pins JP4 with jumper. The mute function is now deactivated.

Sjostrom Audio - PA03 Pavel Dudek's deLuxe Gainclone

Unless you plan on using the mute function, I would jumper JP4, which is under the RE1 relay.

Last edited by loafimus; 19th May 2018 at 09:34 PM.
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Old 20th May 2018, 08:23 PM   #285
Sneeze is offline Sneeze
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Thank you clog and loafimus!

My amp works now. I had jumpered JP4, but with the relais still in place. Then I took a closer look a the pictures of other people that finished their board and saw that a jumper is also needed on the fifth pin of JP1. The moment I put a jumper there, the music started playing I feel stupid now for replacing that whole amp chip..

Quote:
Originally Posted by clog View Post
Besides I see a lot of what seems to be metal particles between the fins of your heat sink. Better to be careful and clean the board thoroughly.
Yes, I saw that too when I took the photo , it's been cleaned up now.

The only problem left is that one channel (the one on 'Out A' of the chip) doesn't sound as clear and loud as the other channel. Tomorrow I will try to clean up the board some more, maybe that helps.

Any other ideas why one channel could be distorted?
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Old 21st May 2018, 01:07 PM   #286
clog is offline clog  Netherlands
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Mmmmm, could be anything. I'm no expert in fault seeking. Some points.

- clean the board, both sides;
- correct components in correct places with correct orientation?;
- check for solder bridges;
- cold joints, when in doubt reflow soldering;
- wiring firmly attached?;
- you checked the test points, right ?. Nothing strange here?

Perhaps one of the other builders with more experience than me can chime in (@loafimus?)
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Old 21st May 2018, 06:40 PM   #287
peranders is offline peranders  Sweden
Electrons are yellow and more is better!
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Join Date: Apr 2002
Location: Göteborg, Sweden
Newbee build: PA03 amp (LM4780)
If both pcb's have the same problem, then you have a building error.
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SSR03 group buy. Sign up for interest HERE. 15 pcb's in order. 0 paid.
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