old school usa - 100 with all wires coming out the amplifier instead of terminals - diyAudio
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Old 27th April 2009, 02:12 PM   #1
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Unhappy old school usa - 100 with all wires coming out the amplifier instead of terminals

I got this amp from a friend and really dont know anything about it as to year model and such. I am looking to repair it and was wondering if anyone might know the board well enough to tell me a few of the resisitor values. I have three burnt resistors r346, r246,r400 and cannot tell the original values on the resistors. Pleease help, i have been reading around on this forum and have found a wealth of information and am amazed at the people willing to help people trying to start repairing their own equipment. I learned about this site from bcae1 website and have been reasearching for anything on this amp but really havent found anything with anything on it with the exception of ampguts which does not have a model as old as this one. Thanks for any help.javascript:smilie('')
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Old 27th April 2009, 05:07 PM   #2
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Default burnt resistors

r246 is at the top of this pic in between the0.1 ohmresistor and the yellow box thingy with the markings E104K*H4R next to right speaker positive(black)

with m eter on diode test itreads 008 and sounds alarm
at ohms it reads .009


all three resistors are green in color and have brown,?,?gold on themt
too burnt to read colors

r346 is at bottom of pic also between the o.1 and the yellow boxnext to the white right speaker-

it has identical readings to r246 being 008, 0.009

r400 is on the bottom right of the picbetween the caps and the transformer

it reads 082 on diode is this correct even though it is burnt?
and .097 ohm

i am currently checking the transistors and tip35's to see if there is any problems thanks to perry and his tutorial for the added confidence to work on this myself considering i dont really have the cash to send it to someone because i havent been at work since nov. when i tore my mcl in my knee . anyone have any suggestions or know anyone who might have a service sheet on this amp(old usa-100) that i could ask about the values of the resistors? any help would be appreciated greatly...also anyone here have a bolt300.4 that they have done work on or a kole audio qx2-980? I have killed both of these a while back and think i am gonna look around and see what i can find. Might as well buy all parts a one time??????? oy yeah thanks for puttin up with a newbie with alot of stupid questions this sight is great.!!!!!!
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Old 27th April 2009, 05:42 PM   #3
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Location: Louisiana
The resistors reading 0.009 (diode check mode, I assume) are likely in series with the yellow capacitors. If so, they are likely connected across the speaker output as Zobel networks. These commonly use 10 ohm resistors and 0.1uF caps. The numbers for the cap that you provided indicate that it's a 0.1uF cap. The resistors may be OK.

0.082 on diode check is likely 100 ohms, not 0.097 ohms. It too may be Ok.

Lightning will likely supply the schematic for the Bolt amp.

The Kole schematic may be available from Power Acoustik. Tell them you want the schematic for a LX2-1000. Don't tell them you want the Kole schematic. The following is the board in the LX2-1000.

http://www.bcae1.com/temp/IMG_0756x.jpg
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Old 28th April 2009, 03:16 AM   #4
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Can you post pics of which heat-sink you have? I have a lot of the early US Amps. Before I pull them apart for you for pics, can you send a pic of which heatsink you have?
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Old 30th April 2009, 02:01 PM   #5
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thanks perry i'll try ligtning and power acoustik tommorrow been busy and havent had chance to do much.


tomtom here is pic of my heatsink been having trouble trying to post pics cause they wont fit
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Old 3rd May 2009, 02:12 PM   #6
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Default bad outputs

I finished testing the tip35c's and both output channels were bad. Also the ones for the power section tested fine but a couple have weak legs on em i gues from bending out from heatsink on removal. Anyone have any suggestions on where to get replacements from they are marked from top to bottom morocco, tip35c, 322 does anyonr know the brand? it looks like a pic of texas with an I in the middle beside the #322. Also what else should I check since the outputs are gone the .1 ohm Resistors?
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Old 3rd May 2009, 02:49 PM   #7
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mouser:
863-TIP35CG

The originals were made by Texas Instruments but they no longer make those parts.

Yes, check the emitter and base resistors. Also check the driver transistors.
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Old 3rd May 2009, 06:06 PM   #8
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The one that you have is the 2nd generation of the US Amps. I have some of the USA50 of that series. I do not have the 100 of that series. Have the original series 100HC and a few of the KA50's.
For the TIP35 and TIP36 , check Ebay. I bought a lot of 50 on there awhile back for cheap. I will take some pics of the USA50 Board for you here shortly, and it might help somewhat... Will post shortly.
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Old 3rd May 2009, 06:25 PM   #9
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Here is the link to the 2nd gen US AMPS 50 board. HQ pic. Might need to play with the contrast and brightness a little. This is one that I was going to repair about a year ago. Still sitting open on the shelf. Also, here is a pic of a US AMPS 100HC 1st gen opened. If you need detailed pics of a specific section, or anything else, let me know...

http://i250.photobucket.com/albums/g...c/P5030317.jpg

http://i250.photobucket.com/albums/g...IO/USAMPS2.jpg
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Old 5th May 2009, 09:06 AM   #10
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Default problems finding rectifier

I havent been able to find anyone with the rectifier gi1402 mouser has it in their book but doesn't stock saying a 10 week wait time I need 2 of them anyone have ideas to a dealer. Ebay doesn't have them either. I figured I might as well replace all of them if i can find any the amp has 4.
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