AMEK Power Supply

imix500 · 3rd July 2006, 04:10 AM

Hello all, I need help with this one. I am repairing an AMEK psu that is for a Scorpion with Uptown Automation. It was thrown out because of a failure and I just had to scoop it up.
Transformer and rectifiers check out fine.
The failure was that two electrolytics exploded in such a way that the un-coiled metal film shorted to the case of the tip32 driver on one and to 0V on the other.
Attached is a schematic that is basically the same, except that both rails use the LM338/2955 and rails are rated for 10A. The caps that went supernova are C4, and one that isn't in the schematic- it is C10 on the pcb. It's across the rail at the output connector and bypassed with a small tantalum cap. Both lytics are 10uf 35v.
The unregulated rails are only ~28v so it wasn't over-voltage if the reg failed. Any ideas as to why those two caps would have blown? Thanks!

PS, is it possilbe for the TIP32 to measure a few ohms in any test lead configuration while in circuit as the pass driver?

testlab · 6th July 2006, 04:43 PM

Age is probably the primary contributor to electrolytic failure.

As these dry out with age and use, the ESR rises and increases the heat rise in the capacitor. This problem feeds on itself until the smoke is released.

My advice is to wholesale replace everything past the rectifier. The parts are relatively inexpensive(< $20 total).

Do you have the console as well?

imix500 · 6th July 2006, 09:52 PM

Hi testlab, I was hoping age was th culprit as it's an easy fix to recap it. Both caps are on the V- Rail side and I thought it strange that both went together. Unless, the first went and no one noticed until the second went.
The console is still around. Know someone that might be intersted?

testlab · 6th July 2006, 10:54 PM

Possibly. What is the configuration? How many auxes?

imix500 · 6th July 2006, 11:16 PM

testlab, I will have to look at it which means digging through all the old consoles no one uses anymore. As mentioned in the first post it does have uptown automation, v1.0 I think.
We're getting a first national tour out the door tomorrow so it might be early next week. I'll will back to you.

CAIO · 30th November 2007, 09:14 PM

Hi, I have a question...why the +V rail is rated 10 amps and the -V onli rated on the 338 current handling???

I need to build a PSU for a Amek/Tac B2, is this psu to big for the B2???

imix500 · 30th November 2007, 11:23 PM

I believe the + Rail was rated at higher current for meter lights, indicators, etc. On the larger PSU's, the rails were both the same rating.

How many channels is the B2? That will give a rough estimate of current draw. The psu in the posted schematic was good for at least 24 channels.

6th July 2006, 04:43 PM	#2
testlab diyAudio Member Join Date: Dec 2005 Location: Grand Rapids MI	Age is probably the primary contributor to electrolytic failure. As these dry out with age and use, the ESR rises and increases the heat rise in the capacitor. This problem feeds on itself until the smoke is released. My advice is to wholesale replace everything past the rectifier. The parts are relatively inexpensive(< $20 total). Do you have the console as well? __________________ It's not whether you win or lose, it's how you lay the blame.

6th July 2006, 10:54 PM	#4
testlab diyAudio Member Join Date: Dec 2005 Location: Grand Rapids MI	Possibly. What is the configuration? How many auxes? __________________ It's not whether you win or lose, it's how you lay the blame.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Split Voltage Switching Power Supply for Power Amp	vectorplane	Swap Meet	2	24th April 2011 12:48 AM
LTspice tool for power amp power supply component evaluation	andy_c	Software Tools	2	23rd August 2009 06:10 PM
is there a circuit for a power supply to power the differant add on clocks	frank2395	Digital Source	1	30th June 2005 10:33 AM
selling high current power supply for power amps.	ericpeters	Swap Meet	0	14th January 2005 03:21 PM
heater supply (xformer specs are 6.3V 2.5A) as supply for a power LED?	jarthel	Tubes / Valves	10	21st July 2003 02:30 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

6th July 2006, 09:52 PM	#3
imix500 Proud Union Member diyAudio Member Join Date: Mar 2004 Location: Putnam, NY	Hi testlab, I was hoping age was th culprit as it's an easy fix to recap it. Both caps are on the V- Rail side and I thought it strange that both went together. Unless, the first went and no one noticed until the second went. The console is still around. Know someone that might be intersted?

6th July 2006, 11:16 PM	#5
imix500 Proud Union Member diyAudio Member Join Date: Mar 2004 Location: Putnam, NY	testlab, I will have to look at it which means digging through all the old consoles no one uses anymore. As mentioned in the first post it does have uptown automation, v1.0 I think. We're getting a first national tour out the door tomorrow so it might be early next week. I'll will back to you.

30th November 2007, 09:14 PM	#6
CAIO diyAudio Member Join Date: Sep 2005	Hi, I have a question...why the +V rail is rated 10 amps and the -V onli rated on the 338 current handling??? I need to build a PSU for a Amek/Tac B2, is this psu to big for the B2???

30th November 2007, 11:23 PM	#7
imix500 Proud Union Member diyAudio Member Join Date: Mar 2004 Location: Putnam, NY	I believe the + Rail was rated at higher current for meter lights, indicators, etc. On the larger PSU's, the rails were both the same rating. How many channels is the B2? That will give a rough estimate of current draw. The psu in the posted schematic was good for at least 24 channels.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)