ampeg v-4 restoration project

[michael_krell]

Hey i just bought an old Ampeg V-4 off of ebay. it is pretty beat up, theres somethings that I know are going to be a challenge. Does anyone have any tips??

I want to redo the decals on the face panel by using toner transfer. is this doable> I planned on using toner transfer and then clear coating it to protect it. I know one issue will be the rust. On the back pannel theres is tons of rust, Im going to attempt to sand some of it down and spray areas with rust, trying to keep the labeling in tact.


if anyone can help let me know.

[michael_krell]

Does anyone have a v4 that they can take the pictures of the inside for me. or possibly know where i can find some. the schematic i have isnt very helpful

[Fret Wire]

Go to the Ampeg section, the V-4 is broken down into power and pre-amp.
http://www.schematicheaven.com/

This link is the originator of Ampeg schematics. He also has voltage charts.
http://home.rochester.rr.com/piazza/index.html

This should help besides the general amp basics: safety, discharging caps, replacing all electo's, checking to see if the factory cut the voltage rating too close on some electro's, etc.

[Doug_H]

For faceplates try this:

http://www.customampfaceplates.com/

A lot of the ax84 people use this or go directly to BNP Laser and are very happy with the results.

Doug

[JimiB]

I have a v4 and a v4b
let me know if I can help

[Fret Wire]

Nice link Doug.  Trophy shops can do simple faceplates ok, but nowhere to the degree of that site. That link's a keeper.

[michael_krell]

Hey JimiB is there any way you can take some pictures of the inside of your V4 so i can see how its wired, I have some things that are disconnected and I am not sure how to reconnect.

The one thing thats bother me is the filter cap all the way on the left side of the amp (looking at the front) next to the output transformer. theres some red and yellow wire remains that are snipped and there is no sign of where they went to or came from. i dont  understand how filter caps work and why they have multiple terminals. in the schematic theres like shapes above them, i dont know what this means. ill post the schematic for you

[AL]

Mmmmmmm Ampegs !!! Great amps and much cheaper than other "vintage" amps.

A quick search and here we go.

http://www.babymonoxide.com/cgi-bin/ultimatebb.cgi   Who knew!!! A V-4 forum.

http://acplink.com/     Amplifier Chassis Pics - Great site with a wonderful pic of the inside of a V-2 ( and a foot - nice nails). It may be helpful.

http://www.ampeg.com/newforum/index.php  Ampeg Forum - may be some help.

http://www.vintageamps.com/PlexiPalaceUBBcgi/ultimatebb.cgi    Plexi Palace - Vintage Amps forums. Check the Other American Amps section.

http://www.firebottle.com/ampage/  Well you can't go wrong here.

Good luck and keep us posted. I've been in a few amps lately and it's been a really good learning experience and a lot of fun. BE CAREFUL - those #$**!  toggle switches bite !!! Unplug Unplug Unplug.

AL

[AL]

What was I thinking!!! I can't believe I forgot this page.

http://www.fliptops.net/

Good info, but more importantly a lot of those ridiculously rare parts Ampeg used.

AL

[Fret Wire]

Can caps are more than one electrolytic cap housed in one unit. Multi-section is a common term. Multi's can be either can-type (usually mounted outside the chassis), like your refering to, or they can look like a radial electrolytic with several leads (usually mounted inside the chassis). They are generally used for power supply filtering, but don't let the term filter cap mislead you. A multi cap is a multi cap.

Looks like you have three can multi's.

C17- which is a three cap multi, 40uf, 40uf, 40uf @ 500v.

C18- which is a two cap multi, 40uf & 100uf @ 450v.

C20- which is a two cap multi, 40uf & 100uf @ 450v.

Take note, and you'll see that most use a common ground, and the pos of each individual cap goes to a different part of the ckt. C20 is an exception as the pos of the 40uf section has no connection. The neg of the 100uf section of C20 is tied to the pos of 100uf section of C18.

Sometimes, a multi will not only have different values for the caps, but different voltage ratings for each individual cap.

At a minimum, a multi will have a positive lead or tab for each internal cap, and a ground lead. Some may have more than one ground lead or tab. If you look closely, some cans and multi radial types with leads, instead of tabs, will have the values for each, plus the color codes on the outside.

Can multi's are not as easy to find anymore with the right values, or original mounting size. They are also more expensive than single caps. Many times if you have the room in the chassis, you can use individual electro's instead of multi's. This is a common method, and with the original can cap left in place, but disconnected, the amp still maintains it's original look from the outside.

A Champ for instance, has a multi can cap. $30 for a new one. A BF/SF bassman has a pan cover on the chassis bottom that has individual electro's under the cover. Much cheaper to replace, and your regular soldering iron will handle it. The can caps that use solder tabs require a high wattage iron because your soldering directly to the chassis, which acts as a heatsink.

Antique Electronics has a pretty good selection of multi's. Look under both radial and can types.
http://www.tubesandmore.com/

Btw, whether it's a multi, or a single electro, every electro (cap or individual section) has to be discharged before working on the amp.

[Fret Wire]

Twist type-usually solders to chassis.


Clamp type- uses a screw clamp that mounts to chassis.


Radial type- usually mounts inside of chassis.



Notice the radial multi: 47uf & 80uf @ 160v. The red wire is the pos of the 47uf section, orange is the pos of the 80uf section, and black is the ground for both.

[michael_krell]

wow that information was very helpfull, thanks a ton.

[JimiB]

let me know if you still need pics!

[michael_krell]

I could definetly still use pics, it looks like the amp was service at one point and some caps were replace by onboard ones and the can all the way on the other side next to the transformer wasnt needed anymore. I could be wrong which leads me to my next subject. I thought i had everything hooked up the way it was supposed to and i plugged the sucker in. Before i could even get a chance to unplug it i noticed a small fire. seems like the bridge rectifier caught on fire. The diodes are completely fried. I did notice some of the  pre amp tubes warming up though so i think it might have been working a little bit. I am also trying to modify this thing for EL34's. It looks like someone started to but never finished. The 470 ohm resistors were replaced with 1K's but pin 1 and 8 were not connected. so i connected them. Could that have done it??? when i got the amp the wires goign to the output transformer were disconnected, maybe this has happened before and the person disconnected it. i dont know.


my question is what would cause this to happen? a short?? Also, how crytical are the filter cap values? they wouldnt cause the amp to catch on fire right? even if there arent any caps there it shouldnt catch fire.

I will check for shorts in the electrolytics.

[michael_krell]

also, what diodes do i use to replace the burnt ones?

[Mike Burgundy]

Not a big help, but a bassist I used to work for has a V4b. If anything is missing from the picture the others paint, I might be able to get re-acquanted with that amp.
Just make sure you use tubes that can stand high-voltage abuse. A lot of these are "converted" to 6L6 - you might want to consider this as 7027's are progressively harder to get if at all.. If memory serves, however, that amp ran higher than the spec 340 or 350 Volts,  rather pushing the tubes.  Don't be afraid to run it cold. I know this sounds strange, but we tuned it by ear, started at slightly under the "70%" rule, and turned down a LOT until it sounded just right. I can't remember what the current was, but I do remember marvelling at how *low* it was while the amp sounded so good.
hih

[michael_krell]

im actually looking at these diodes now, they really dont look like they can handle the power. I have some other diodes that are about the same size and the maximum they can handle is 1.5 amps. it would be nice if i can get a pic of someones circuit board so i can the diodes they have. I might just go to radio shack and get some 6 Amp rectifier diodes. For some reason the specs on them say only 50 PIV. is this OK?

[vseriesamps]

hey michael

i'm sorry i can't answer your diodes question but our bass player does have a V4-B and I have a digital camera. I'd be willing to take some shots of it if you still need them. Just PM me.

Awesome. Long live the Ampeg anything.

K
certified Gem I user

[usbdevice]

Hey Michael

The rectifier diodes on my VT-22 are marked SI 555-2 (the VT-22 is the combo version of the V-4).
Mine is a 1975 model.
Hope this helps.

Cheers
Lenny

[michael_krell]

Yes it does help alot thanks. I have another question. it seems to me that this thing has been butchered in the wiring department. looks like i need to rearrange some things. what does PL stand for on the schematic? is that the standby light. i have a feeling that is it. Also there is a a big white, what looks like a wire wound resistor strapped to the bottom of mine. what is this for and if it is a resistor, where does it go to.