1973 Marshall Lead/bass 50w Head

[DorsetLad]

Hi there,

Was after a bit of advice really.

I own what I believe to be a 1973 Marshall Lead/Bass 50w head (photo hopefully attached).

I was in a band in the 1980s and I used it a bit then, but sadly has been mainly sat in a cupboard under the stairs since then. Yes sacrilege I know, but although I still play a bit, it's only ever in the back bedroom for which I use a small practice amp.

Anyway I have decided that I really need to do something with it. It's in fairly decent nick for its age. It's fully operational, although there is a reasonable amount of background buzz when plugged in. There are some small tears in the covering, and a couple of the knobs are cracked and missing their gold tops. As I said it's been under the stairs for 30 odd years and never serviced in that time.

So my questions are, have I correctly identified the model ? How much roughly might it be worth, and what are my options re getting it serviced ? I work in Oxford but live in Dorset, but not sure if anyone in those areas does that sort of thing.

Many thanks in advance for any advice given.

Cheers, Dave

 

[neikeel]

Hard to tell exactly as it hs been modded (the extra pots in channel 2 input jack holes and an extra switch with the lamp bing moved across).
Need pics of the serial suffix and the insides (chassis top and boards) to give full overview.
The white piping around the front panel only happened like that in '76 but I would expect elephant vinyl.

 

[Marshallhead]

I've seen a few 1973 heads with factory original white piping - not many but enough to think some were churned out like that. My first Marshall was one in fact!

 

[neikeel]

I ve learned something again!

 

[DorsetLad]

Hi there, thanks for the responses. Here are a few pictures on the internals. Cheers, Dave

 

[neikeel]

Looking good so far, now for pics with the chassis out.
If you look at your bottom picture inside the head cab there is some wiring (red and pink with parts attached to it - is that part of the mods?).

 

[DorsetLad]

Hi there,

I have to be honest that I am not really comfortable taking the amp apart any further than taking the back off. As you may have gathered I don't really know what I am doing and knowing my luck I am liable to break something ! Whoever did the mods, it wasn't me, so this must have been done before I owned it.

I have been having a look, and there are various places that might be able to service the amp in the Oxford area (including by the looks of it the Marshall place at Bletchley, which isn't too far away). I am assuming that a service would include replacing the valves, and that getting this done is not going to cheap ? Any idea what sort of ballpark figure I might be looking at for this ?

Cheers,

Dave

 

[neikeel]

Hi Dave
Problem with taking it to Marshall is that they will want to change the ac input to an IEC that involves cutting and drilling the rear panel. Makes it giggable in those places that PAT inspect gear but devalues it.
Removing the chassis is easy:
Place the amp face down on the floor. Unscrew the four pozidrive screws on the bottom (the nuts are captive in the chassis).
Put your hands around the ends of the chassis and lift it out. Place it on a desk or bench with the circuit board upmost. It willl sit relatively stable on the mains and output transformer.
An old forum member Damien Beale lives Oxford way. He may be able to help if he is locateable!

 

[DorsetLad]

Ok thank you - I will have a look at it when I get home tonight and see if I can post some more photos then.

 

[liontato]

Those valves may be absolutely fine. If it plays I would sell as is. Take some pictures of the inside. Do a sound clip and sell it. The next person can do all the maintenance. If you have work completed make sure you get the original parts back.

 

[DorsetLad]

Ok so had another look at the inside of the amp last night.

I was going to remove the chassis, but on closer inspection there is a component (which I think is the "mod" mentioned earlier) on the right hand side of the case (as I look at it from the back) which is wired to the main board by some very delicate looking wiring. So I really don't want to mess with this in case I break something, so I didn't attempt to take the chassis out.

I did, however, attempt to get some more pictures of the inside of the unit. There is a sticker in there with some further details on it, and it does appear to confirm that its from 1973. It would be interested to know what the "mod" is as well. Sorry if some of the pictures are a bit blurry but there isn't much room to work with !

Cheers,

Dave

 

[neikeel]

Looks to be a small transformer with diodes mounted on top.
Could be a mod for dc heaters or a regulated dedicated psu for a foot switch.
On a 100w amp you could explain it as a bias feed if the PT bias winding were dead but these feed off the JT secondary.
Very interesting for me/is but does not help with value.
People like clean and original with no mods. Preferably a lead amp with turretnoatd, no extra holes.
Not to say it is not worth a reasonable price but not top££.
I would go ebay with. 99p no reserve and lots of clear well lit pics. But you will need board shots Otherwise everyone will be guessing.

 

[danfrank]

Those valves may be absolutely fine.

I second this opinion. They look to be in pretty good condition from your pictures. Don't let the flaky white lettering on the tubes discourage you; this happens to many old European tubes.

 

[Kris Ford]

What exactly makes "Lead and Bass" spec?

 

[neikeel]

It is a bass amp with a big 5000pF cap on channel 1, that is it!

 

[JeffH]

Don't power that amp up without speakers plugged in and the impedance selector is missing the plug to select output impedance. It's possible it's wired internally.

You could unscrew that external transformer "thing" first and then remove the chassis. That will be the best way to see what's been done.

 

[Trapland]

If you weren't comfortable taking the chassis out, definitely don't. Especially after seeing that thing hanging out there, who knows what deadly voltages may be easy to touch. Also if it hasn't been plugged in for 30 years, please don't until it's been serviced. It really needs service at least to verify the filter capacitors are working.

Service it and play the crap out of it.

Or sell it as is.

It's about a net wash. It is worth a fair amount less because it's modded and needs service. But if you pay to have it serviced, you'll have cash out of pocket AND a formerly modded amp. It's a good amp, it deserves some love.

 

[Pave Dog]

Ok so had another look at the inside of the amp last night.

I was going to remove the chassis, but on closer inspection there is a component (which I think is the "mod" mentioned earlier) on the right hand side of the case (as I look at it from the back) which is wired to the main board by some very delicate looking wiring. So I really don't want to mess with this in case I break something, so I didn't attempt to take the chassis out.

I did, however, attempt to get some more pictures of the inside of the unit. There is a sticker in there with some further details on it, and it does appear to confirm that its from 1973. It would be interested to know what the "mod" is as well. Sorry if some of the pictures are a bit blurry but there isn't much room to work with !

Cheers,

Dave

Dave, I realize this is a really old thread, but what did you end up doing with the amp?