Powerpod 740 blowing fuses at powerup

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#22
ShorBird said:
Sisko -
I have been unable to secure a service manual for the deluxe model with the digital effects display unit, but all other parts of the amp are covered by the older schematics I have. I will email you a copy.
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Thanks! Really apreciated.
Ive found the whole service manual, the one wich has the DSP and stuff. Its 40 pages and 56mb.

So if anyone needs it, just give me your email
 
#25
Sorry to bring this thread back up but I was wondering if I could get the schematics for the Phonic powered mixers (i have the older 1062 model). I have the ever common bad channel and would like to get this thing working again.


my email is disassembled @ yahoo.com


Thanks,
Greg
 
#26
Shorbird, when you contacted with Phonic do they gave you some kind of explanation about waht its causing the problem?
I repaired one unit and it broke again.
From the sintoms (blown ic literally) i can guess that its some kind of parasite oscillation (maybe a poor pcb desing). Or the Igbts are becoming shorted and high voltage is induced to the ic, but the question is why?
Do you have any information about this?
 
#27
Nope, sorry. They sell a 'kit' to help solve the problem with the switcher, which has quite a few parts including IC's, transistors, diodes and resistors. It takes about an hour just to install all the stuff, but none of it seems different from what was already in there. I would suggest emailing them with your question.
 
#28
Hi,

Something to look out for if you've got a dead channel is fake transistors. Whilst repairing mine a couple of years ago I replaced numerous blown/burnt components and under light testing everything looked OK. After cranking up the volume to about 20W the o/p semis blew. I eventually discovered they were fakes even though they came from a reputable supplier.
There's a thread on this board about it if you search.

Good luck
Bob
 
#29
Yes, Im aware of those.

Sadly in my unit the parts that blows is in the swiching supply. My toughs is that there are some kind of high frecuency parasite oscillation due to a poor pcb design.
1) Phonic has a kit already for this.
2) Ive seen a large number of reviews like this, despite many more people dont say this because they dont have internet acces, or just simply made their unit garbage.

The solution that ive found is making a analog transfomer, im building it right now, but have some troubles with the secondary bobin.

Ill tell you any news i have.
 
#30
Hi Sisko,

Does your model have a switch mode supply?
I thought they all had transformer PSU's, heavy but reliable.

Just a thought if it is switch mode, you are probably aware of bad electrolytic capacitors that have plagued all types of kit over the last few years.

Good luck
Bob
 
#31
Yes, it has.
I think they move to SMPS because of the money, but they did a bad homework there. I repeat, I think the problem its due to a poor pcb desing.

I didnt know about the electrolitics neither ive measured them but in my case, the power IGBTS where always in short and the controller IC was burnt or broken (exploded)after some use. They were from diferent suppliers every time i change them.

This SMPS has protecction everywhere, wich traduces to tons of loops and feedbacks on the pcb. Those may be the problem😡
 
#35
Yes there are 2 versions of the powerpod 740: the earlier black carpet covered ones with push-button effects and the later vinyl ones with digital display. The early ones have a standard transformer PSU and the later have SMPSU. The output stages are rather complicated class-H device; the fets are the rail switches. If the FETs fail, its often because the bipolars have gone as well, and often causing multiple domino-effect failures throughout the board. These are not to be confused with FEts in the SMPSU.
 
#40
Blown Switch-mode PSU

Hi,

I have one of these units with the IGBT's shorted in the PSU.

I'd like to get a copy of the schematic so I can check for whatever caused the big devices to fail before I turn it on and fry the replacements. ( RSwww - about £3 each )

None of the power transistors in the amplifiers appear to be shorted, so I'm hoping it's just the PSU that's died.

I notice that someone has managed to get a response out of Phonic - even some spare parts - does anyone know what there is in the repair kit?

If no-one can e-mail me the schematic, does anyone know what the supply voltages should be?

Thanks, Graham.
 
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