1969 Ampeg SVT Restoration Thread

[Chris 'Wighat' Jordan]

As Tim said. You have to remove the jacks, pull the pots back, remove the lamp and two switches. With everything out of the way, the face panel slides out.

If you google "RAL color chart powder coat" or "RAL powder coatings" you can see what is available in terms of color. Coatings are rated for different applications. You want indoor/outdoor weather resistant. I request Slate Grey 7015. It isn't a match for what was used originally but I like it, I prefer a darker grey. If you bring in the original panel they should be able to match it. If they have to order a custom color, it could cost more because they have to buy a large container. I find that they often have something close that will work. The ones in the pic below may have been a darker color.

This is a stripped panel. The high ridges are sanded (scraping can chip the edges) to reveal the metal. I get the painter to run his finger over the coated edges after they are sprayed with the powder. This leaves very little to remove once it had hardened. I find that often these panels need some sanding on the ridges. They often have dings that can be sanded out with a block and made to look better. Specify that you want the inside edges of the cutouts painted, they spray the back in those areas to ensure coverage.

One note about powder coaters. Prices can vary quite a bit so it pays to shop around.

The black panel below is the original one from a V4B. I wound up replacing it with one from fliptops.

View attachment 703716 View attachment 703717 View attachment 703718 View attachment 703719 View attachment 703721


The ridges in the image above are before sanding. If you look closely you can see some paint misting over some of the areas.

Very good! If I wanted to "dress" or sort polish-up the face plate with the recessed blue graphics, how would you recommend that be done? Or should it not be attempted?

I would be interested to see a pic of an unmolested, all-original '69 back panel please if anyone has one. Didn't they originally have a 4-pin XLR connector for the speaker out?

I intend to restore mine with a repro from Fliptops even though the '69's didn't have the graphics, it looks great and is reversible. Also mine has a couple holes tore in it and that'll help cover that up.

 

[Chris 'Wighat' Jordan]

And one more question while I'm thinking about it: were the plate cap/connectors on the early SVT's little black bakelite numbers like this? Or something else. How does the wire attach in side the cap on the originals, etc? Did yours still have the original plate caps when you got it @JimmyM ?

 

[Chris 'Wighat' Jordan]

OK, I'm just going to post thoughts and questions with reckless abandon, secure in the faith that those in the know will chime in at some point.

It looks like the extension speaker jack was 1/4". The cabs had the four-pin jack. Did one have to get a special 1/4"-to-4-pin cable to hook up the second 810?

Am I crazy to want to restore the 4-pin system? Wouldn't that have B+ voltage running through it? That sounds quite dangerous.

I doubt I'll ever sell this amp but I do want to do right by it in terms of restoration. I feel okay about replacing all the PCB components. I really don't think there's much fuss over factory-original resistors. But what about the various pots? From a practical standpoint, I would want to replace them - but on the other hand, they are part of what authenticates this amp as being a true first run SVT.

 

[beans-on-toast]

Very good! If I wanted to "dress" or sort polish-up the face plate with the recessed blue graphics, how would you recommend that be done? Or should it not be attempted?

I would be interested to see a pic of an unmolested, all-original '69 back panel please if anyone has one. Didn't they originally have a 4-pin XLR connector for the speaker out?

I intend to restore mine with a repro from Fliptops even though the '69's didn't have the graphics, it looks great and is reversible. Also mine has a couple holes tore in it and that'll help cover that up.

I've done it but you have to be really careful. I use fine sandpapers tightly wrapped around a thin rubber block that I buy from an auto body supply shop. Lightly wet sand with a drop of liquid soap. The block sucks down onto the surface. The higher surface is sanded, the recessed blue is not. Sand along the length of the plate. Once you start sanding, you have to do the entire surface. It can clean up the faceplate nicely. It can also destroy it.

Yes they had a speaker cable with a four-pin connector on the end.

Check the dimensions of the fliptops repro back panel, the cutout holes may not align.

This is the back of a '69. The wire solders on to the plate cap clip. The originals had a little bump out on the top.

 

[Chris 'Wighat' Jordan]

I've done it but you have to be really careful. I use fine sandpapers tightly wrapped around a thin rubber block that I buy from an auto body supply shop. Lightly wet sand with a drop of liquid soap. The block sucks down onto the surface. The higher surface is sanded, the recessed blue is not. Sand along the length of the plate. Once you start sanding, you have to do the entire surface. It can clean up the faceplate nicely. It can also destroy it.

Yes they had a speaker cable with a four-pin connector on the end.

Check the dimensions of the fliptops repro back panel, the cutout holes may not align.

This is the back of a '69. The wire solders on to the plate cap clip. The originals had a little bump out on the top.

View attachment 705140 View attachment 705141

View attachment 705142

Awesome! I think I can find some like that. You're, right, Mr. Toast: I can see right away the Fliptops backplate's cutouts don't line-up. Esp the main speaker cord hole in relation to the Ext. Amp jacks. I guess mine is going to stay all prototypey.

Found a pic of an early SVT with what appears to be a gray or silver back plate with printed graphic labeling. This is a new one on me.

 

[beans-on-toast]

It looks like the extension speaker jack was 1/4". The cabs had the four-pin jack. Did one have to get a special 1/4"-to-4-pin cable to hook up the second 810?

Am I crazy to want to restore the 4-pin system? Wouldn't that have B+ voltage running through it? That sounds quite dangerous.

I doubt I'll ever sell this amp but I do want to do right by it in terms of restoration. I feel okay about replacing all the PCB components. I really don't think there's much fuss over factory-original resistors. But what about the various pots? From a practical standpoint, I would want to replace them - but on the other hand, they are part of what authenticates this amp as being a true first run SVT.

How far you want to restore the amp is up to you. No need to change the pots unless there is an issue. I would leave them, like you said, they have date stamps.

It is safer not to use the four pin-connector. The safety circuit in the connector was wired differently, depending on the amp. If you install a ¼" jack in place of the able, use insulating washers so that the ground doesn't contact the chassis. Use a pair of Switchcraft S1028 and S1029 washers to mount a jack with a shorting shunt, Switchcraft 12A. Adding a jack in place of he speaker cable was a common mod, even back then.

There was a special cable for the extension cab.

 

[JimmyM]

And one more question while I'm thinking about it: were the plate cap/connectors on the early SVT's little black bakelite numbers like this? Or something else. How does the wire attach in side the cap on the originals, etc? Did yours still have the original plate caps when you got it @JimmyM ?

View attachment 705064

Yes it did, but now it's missing one original one. Mine were white. Don't know how they attach, though.

 

[Chris 'Wighat' Jordan]

The place where the power cord was originally on mine has been cut into a large hole to accept a round, panel-mount, 3-prong AC outlet. The original AC accessory outlet was enlarged to accept an IEC power cable jack.

I can exert all of my welding/metal working skills, patch the hoes and cut them out to original spec's or I can just roll with it, leave the IEC jack and put a flanged 3-prong AC outlet in the round hole to spruce it up a little.

 

[JimmyM]

I'd leave it myself.

 

[beans-on-toast]

Any amp with dangling power and speaker cables is harder to handle. Nothing wrong with a jack and IEC connector. At the same time, those holes would bother me.

I suppose one question would be, could the patch be done without causing further damage. A good pro could do it and grind the outside welded surface flat. But that could be expensive. Not sure if there is room to grind the inside seam or if it would need to be done.

Tough choice.

 

[Chris 'Wighat' Jordan]

Any amp with dangling power and speaker cables is harder to handle. Nothing wrong with a jack and IEC connector. At the same time, those holes would bother me.

I suppose one question would be, could the patch be done without causing further damage. A good pro could do it and grind the outside welded surface flat. But that could be expensive. Not sure if there is room to grind the inside seam or if it would need to be done.

Tough choice.

I am confident I could patch and grind but the damage is done - I might as well leave the outlet and the IEC receptacle. It is practical.

Is it a fact that first run SVT's had neither the PCB cover plate not the labeled back plate?

 

[beans-on-toast]

Is it a fact that first run SVT's had neither the PCB cover plate nor the labeled back plate?

The ones that I've seen: Yes to no power amp cover plate. The chassis had the lettering on the front. The back of the chassis had the removable labeled plate.

 

[Chris 'Wighat' Jordan]

The ones that I've seen: Yes to no power amp cover plate. The chassis had the lettering on the front. The back of the chassis had the removable labeled plate.

That settles it then. I'm going to patch the chassis as necessary and use the Fliptops repro back plate. The only thing steering me away from this to begin with was the assumption that the earliest amp's did not have the back plate. I have seen many of them with out it.

 

[beans-on-toast]

See post 44, the first Image is a 69 with a back plate. I'm not sure how far off the fliptops plate is. To make it work, you might need to cut new holes in the chassis. I've often wondered how difficult it would be to make a back plate. Perhaps have the lettering laser etched into the metal. Infilling with white water based acrylic paint is easy. You'd have to generate the graphics.

It is true that many are missing that plate. This is where they had the company name, the regulatory agency sticker, etc. so you'd expect it would be there.

 

[Chris 'Wighat' Jordan]

See post 44, the first Image is a 69 with a back plate. I'm not sure how far off the fliptops plate is. To make it work, you might need to cut new holes in the chassis. I've often wondered how difficult it would be to make a back plate. Perhaps have the lettering laser etched into the metal. Infilling with white water based acrylic paint is easy. You'd have to generate the graphics.

It is true that many are missing that plate. This is where they had the company name, the regulatory agency sticker, etc. so you'd expect it would be there.

Not to mention indicating the jacks' function. Yes, it occurred to me that I may have to patch and re-cut holes. It might be simpler all the way around to remove the entire back of the chassis where those holes are, weld in a clean new piece and cut nice, neat factory-correct holes.

 

[beans-on-toast]

Not to mention indicating the jacks' function. Yes, it occurred to me that I may have to patch and re-cut holes. It might be simpler all the way around to remove the entire back of the chassis where those holes are, weld in a clean new piece and cut nice, neat factory-correct holes.

I was thinking the same thing, weld in a new back. I wonder if a tig welder would be needed for a job like that.

 

[Chris 'Wighat' Jordan]

I have sent pics and a request to an associate at a specialty stainless steel fabrication shop. He recently did an AMAZING job of making me a commercial sink built into the middle of a long countertop (all SS). Beautiful, seamless, perfect finish with rolled edges etc. I have my fingers crossed he'll help out with the SVT chassis.

There's a power and speaker cord from a B15 on Ebay: Vintage Ampeg B 15 Guitar Amp Power Cord 4 Pin Speaker Cord | eBay

Are these also correct original cords for an SVT @beans-on-toast? Or can I build faithful new ones? The rectangular strain relief on the SVT is what worries me. Is that available?

 

[beans-on-toast]

The cord does not have the original plug. The original was a two conductor cable with a molded on plug. It is good to install a three conductor cable. I have some info that I can send but I have to run for now.

I think that doing a completely new chassis is a fantastic idea. You can keep the original without modifying it. You can get the fabricator to do a back plate as well.

 

[Chris 'Wighat' Jordan]

The cord does not have the original plug. I have some info that I can send but I have to run for now.

I think that doing a completely new chassis is a fantastic idea. You can keep the original without modifying it. You can gwt the fabricator to do a back plate as well.

I proposed to this fabricator to preferably patch the holes, alternately replace the modified section of the original chassis. Either way, I have decided to have it electro-plated or powder coated so the repairs will not be visible in the least.

The notion of a whole new chassis did cross my mind. I know my guy could replicate it perfectly down to the last detail....even make it out of stainless steel. On the one hand, there is absolutely nothing special about that original piece of bent sheet metal, on the other hand....there is!

 

[beans-on-toast]

So many decisions to make. In any restoration, it comes down to how much you want to put into it. You can make it exactly as it was, improve on it, do just enough to make it work. At some point, you realize that you have more in it than you can ever get out of it if you sold the amp. At that point you are doing it for the technical challenges, because you are learning a lot, and for the love of doing this sort of work. There is so much involved. It runs from woodwork, cabinetry, upholstery, and metal work. The electronics is a whole other subject full of challenges and there's a lot to learn.

There is some information on the 4-pin connectors, cable, and Heyco bushings in the TalkBass Portaflex Wiki here: Technical - Amplifier - TalkBass Wiki

For the for-pin connectors I recommend that you use Switchcraft A4F and C4M connectors. For the 18 gauge four conductor cable, I use Belden 8454. In the past I've bought this cable from Surplus Sales of Nebraska but they are currently out of it. Other places sell it.

The bushings used to attach the cables were often made by Heyco. Details are in the Wiki. I find that on some amps, the holes have been enlarged and a different sized bushing is needed. Heyco (Strain Relief Bushings | Power Cord Strain) is still in business producing many of the same parts. The size of the bushing is based both on the cable diameter and the chassis hole size. Check out their web site. Samples are available from them and you can request different sizes so you can figure out what you need. Not sure about finding the square molding that was on the chassis power cord. My '71 had the same round bushing listed in the Wiki.

The Portaflex Wiki also details how to make adapter cables: Tips & Tricks (including modifications) - TalkBass Wiki.

For the power cord, I use Carol brand made by General Cable, 3/18 rubber jacketed cable (see attached, 01311). It is the same size as the original so works with the original bushing and chassis hole. I used to buy it at Home Depot but it seems that it is no longer available everywhere. Other places still sell it though, Walmart lists it (CAROL 01311 Service Cord, SJOOW, Black, 18/3, 50 ft. - Walmart.com For the plug, I buy a heavy black Leviton plastic plug from HD. This one: Leviton 15 Amp 125-Volt Rubber Grounding Plug-R60-515PR-000 - The Home Depot.