Schematic for Ampeg VL-503 combo?

Ken · Posted: Sat Jun 16, 2007 3:52 am Post subject: Schematic for Ampeg VL-503 combo?

Hi, does anyone know where I can get a schematic for the Ampeg VL-503 combo? I've been looking online but to no avail. I'm new to this site and I just bought this combo and the reverb doesn't work. I am knowledgeable in electronics but I'd like the actual Circuit schematic. Thanks and God Bless for all information. Sincerely, Ken Truckenmiller[/b]

erniebull · Posted: Sun Mar 16, 2008 8:57 pm Post subject:

I'd be interested in shematics too !

lancebug · Joined: 19 Mar 2007 Posts: 5 See this user's pet

I'd like to have a set on hand as well. Any leads yet?
-L-

erniebull · Posted: Mon Mar 24, 2008 12:44 pm Post subject:

Me too !!!!!! :D

Russel · Joined: 05 Mar 2007 Posts: 4 See this user's pet

That schematic was hard to track down. You can get it here, but I don't know if the price is still the same:

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The part number for the manual is SM-VL503, and the price is $9.95, plus
shipping. To order online, click here http://www.studiosoundelectronics.com/manualentry.htm and enter the part number and price manually. This will enter the part into your shopping cart. Then proceed to our online checkout.

Studio Sound Electronics ORDERS ONLY 1-800-727-4287
3404 Greenview Drive FAX ORDERS 1-812-949-7743
New Albany, IN 47150-4229 "Your Source for VCR Parts"

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BM · Posted: Fri Mar 28, 2008 11:18 pm Post subject:

I have the owners manual if anyone wants it

Russel · Joined: 05 Mar 2007 Posts: 4 See this user's pet

I just want to clarify that the "manual" from Sound Studio Electronics is actually the schematic. It is not the owner's manual. It also comes with a technical bulletin that addresses how to fix the biasing problem common to the VL-503.

erniebull · Posted: Thu Apr 03, 2008 7:55 pm Post subject:

Do you have this manual , could you send it ?
Thanks

MarXway

[quote="Russel"]I just want to clarify that the "manual" from Sound Studio Electronics is actually the schematic. It is not the owner's manual. It also comes with a technical bulletin that addresses how to fix the biasing problem common to the VL-503.[/quote]

Can you explain the actual bulletin and bias problem? I just bought one of these and it came with all of the VL's schematics and original manual (sweet... I know), but there is no mention of a bulliten. Thanx! Mark
_________________
MarXway

Russel · Joined: 05 Mar 2007 Posts: 4 See this user's pet

The bulletin is from one of Ampeg's engineers, dated Feb. 18, 1994. It says the problem only exists for 503's made before Feb. 1994. Basically, the amp can go out of bias and the problem could be due to the following:

(1) the metal bracket on the rear inside chassis that limits movement of the bias and hum balance trim pots can touch the leads of the pots, and / or

(2) a bad ground connection from pcb's to the chassis.

They redesigned the bracket after 02/94. You might be able to order the revised part. I think (but, could be wrong) the part number is 51-503-71 Rev. 1.

A hand drawn diagram was also included in the bulletin that shows a modification you can make to improve grounding. It shows a ground wire that goes from one of the nuts on a power tube socket, to one of the nuts on the second power tube socket, then continues to the ground terminal point on the power supply pcb. The nuts to use are:

(a) On the tube socket nearest the PS pcb, use the nut closest to the PS pcb.

(b) On the tube socket farthest from the PS pcb, use the nut farthest away from the PS pcb.

I believe someone has a deja.com link in one of the VL-503 posts here in this forum that goes into great detail about the bias problem and how to fix it.

vintagekiki · Joined: 10 Jul 2008 Posts: 3 See this user's pet

I'm looking for schematic Ampeg VL 503.

Thanks

vintagekiki@yahoo.com

vintagekiki · Joined: 10 Jul 2008 Posts: 3 See this user's pet

Grazie molto per i disegni schematici VL503 di Ampeg

Lee Jackson Metaltronix Amplifiers

Schematic for Ampeg VL-503 combo?