Vox Escort 50 Lead... Help needed.

[paulnic]

Hello all,

I've been given an Escort 50 Lead combo, which needs a little 'tweeking' to get it sounding as it should and was wondering if any of you could offer some advice.

When I first recieved the amp it was dead, and knowing very little about amps or related electronics i handed it over to a friend of a friend to get working for me, which he did for the cost of a four pack of beer! Unfortunately it just doesn't sound right. It's extremly basey sounding and has very little of the high frequencies.

I've brought it into work as we have some very knowledgable electronics guys here, but i'd like some information like a schematic for it. I can't seem to find one anywhere. I'm starting to wonder if VOX used the same amp section from another product?

From what i've read, this amp dates from around 1980, could anyone confirm that?

I can't put this in to a proper repair person as funds are tight. so I'd appriciate any advice.

Thanks,

Paul.

Here's a couple of pictures of it...

[Robert M. Martinelli]

Hi,
I'm more into Vox valve amps, but I can confirm the amp has been designed during the "Rose-Morris" period ( late '70s ), unfortunately the S/N ( paper ) tag on the rear panel is missing; however, if you open the amp, chances are you'll find another identical S/N tag inside. I own a ( circa ) 1980 V15 and the S/N is in the 170000, if this can help you in dating your amp.

As to the electronics, I'm pretty sure at least the power output stage should match the one found in the "Escort 50 bass" version; chances are the preamp is similar to ( or the same ) the one the "escort 30 lead" has. All in all a very simple amp, some "small" BJTs and a couple of "big" ones ( 2N3055 ).

try this links

http://www.schematicheaven.com/voxamps/esctb50.pdf

( escort 50 bass )

http://www.freeinfosociety.com/elect...26eaeb3dc0e3fa

( escort 30 lead )

They should be enough to point you in the right direction.

hope this helps

Best regards

Bob

[paulnic]

Hi Bob,

Thanks for the informative and fast reply.

I've opened the cab, but can't find any serial numbers. Looking around inside, it looks like someone's had a go at practising their soldering. There are terrible joints that are just about holding, and some which certainly look dry so I think I might resolder all the bad looking joints first. Can't be a bad thing to try i suppose?

I'm going to add some photo's to show you what i mean..

[Robert M. Martinelli]

Aw!

Looked at the pics, I understand what you mean

Well, the good news is your amp has what seems to be an op-amp, so it's more likely for the "escort 50 bass" schematic to match your amp almost entirely, I would only expect some differences with some caps/resistors to deal with the different tonal range....

Fixing the badly made solder joints is good, but, unless some connections are wrong,( cross check with the schem ) it won't fix your problem....

The amp is almost 30 years old, so maybe it's a good idea to renew all the PCB solder joints ( removing the "old" solder first sucking it with a manual solder remover or de-soldering station and then re-soldering with "fresh" one ), check electrolytic caps for aging, capacitors for leakage, resistors for drifting away from their nominal value, check pots for "normal" operation/value....all these factors can shift the amp frequency response and cause the amp to sound "dull".

Hope this helps

Best regards

Bob

[paulnic]

Great, thanks again bob, I'll get to that as soon as i can and let you know how it went.

Cheers,

Paul.

[paulnic]

Ok, So I went through all the points/checks that bob sugested, and everything seemd to be fine. There were some bad points in there like earth connections that weren't screwed down properly, and some general bad soldering that someone had done at some point in the amp's life. But the most important thing was the components that the person who 'repaired' the amp had used.
There were two transistors that didn't look quite right to my colleague for use in an amp. They were TIP41c and 42C trannys, which i'm told are pnp, npn. A push/pull type arrangement I think?
So, using the schematic pointed out by Bob, I ordered two trannys (BD537 & BD538), and fitted them. I also changed the power switch becasue one of the pivot nibs had snapped and the LED's no longer worked. Luckily we use those switches in work, so it cost nothing.

I must say that i'm very nicely surprised by the amp now.. It sounds sweet and mellow untill it's turned up then it's got a nice raw sound to it.

Seeing as the amp works well, i'm now going to refurbish it with a new grill cloth and VOX logo badge. Seems a shame not to as the amp is in pretty good condition considering is 30 years old and lived a fair part of it's life in a heavy metal band!

I think i'll post a picture of it when it's finished (shouldn't be long!).

Thanks again for the help, this has sparked an interest in electronics... starting to look at making a wah pedal...

Cheers,

Paul.

[Robert M. Martinelli]

Ok, So I went through all the points/checks that bob sugested, and everything seemd to be fine. There were some bad points in there like earth connections that weren't screwed down properly, and some general bad soldering that someone had done at some point in the amp's life. But the most important thing was the components that the person who 'repaired' the amp had used.
There were two transistors that didn't look quite right to my colleague for use in an amp. They were TIP41c and 42C trannys, which i'm told are pnp, npn. A push/pull type arrangement I think?
So, using the schematic pointed out by Bob, I ordered two trannys (BD537 & BD538), and fitted them. I also changed the power switch becasue one of the pivot nibs had snapped and the LED's no longer worked. Luckily we use those switches in work, so it cost nothing.

I must say that i'm very nicely surprised by the amp now.. It sounds sweet and mellow untill it's turned up then it's got a nice raw sound to it.

Seeing as the amp works well, i'm now going to refurbish it with a new grill cloth and VOX logo badge. Seems a shame not to as the amp is in pretty good condition considering is 30 years old and lived a fair part of it's life in a heavy metal band!

I think i'll post a picture of it when it's finished (shouldn't be long!).

Thanks again for the help, this has sparked an interest in electronics... starting to look at making a wah pedal...

Cheers,

Paul.

Hi Paul,
I'm truly glad you sorted it out, but I don't think the problem was due to the two transistors you replaced, as they're indeed pretty close to the ones you installed ( the BD537/588 complementary couple is 80V/8A while the TIP41C/42C c.c. is 100V/10A ). These two pnp/npn are used in your amp as drivers for the power transistors, and cannot have such a big impact on sound.....I suspect your amp's tonal improvement to come mostly from the soldering/rewiring work you've done. Solder joints can oxidize over the years, and renewing them all is surely a good idea.

As to the way the amp sounds, I seriously think that SS Vox amps were good sounding amps, they surely were good value for the money, and they deserved better luck than they had.

I own a '64 AC30 TB, and I also own an AC30SS and, though not as close as the "original" as its name would suggest, the AC30SS is a nice,sweet and good sounding amp.

Looking forward to seeing the pics, don't forget to post them once the amp restoration project is completed!

Cheers

Bob