Nolan 'Studio Session 50' amp head speaks again

Rocker

Back in the mid 1970s, I had a pub band.  Played mostly country, Irish country and country rock.  The music that people could dance to or sing along with.  My fellow guitarist bought a Nolan 'Studio Session 50' head from Pat Nolan in Co. Westmeath.  Pat had spent some time in London and while there, he built a number of amps [AFAIK copies of Fender amps].  Google Pat Nolan for more info if you are of that type. To get back to the Session 50, it was paired with a H&H 4 * 12" cab and the combo made a great sound - exactly what our band needed in fact.  I, as the other guitarist and vocalist in the band, used a 50 watt Marshall head and a Marshall 4 * 12" cab [straight not the angled type].  Neither amps gave us a bit of trouble despite being dragged all over the Midlands of Ireland in a car trailer and often spending the night in the trailer!

A couple of years ago, my friend discovered his amp head in the garage where it had been 'stored' for about 35 years.  His H&H cab had long since fallen apart and so he offered the amp to me for free.  It sat in my garage for well over a year while I considered what to do with it.

Both EL34 output valves looked blown, both had a grey colour like a leaky light bulb.  I removed the chassis and it looked in great condition.  I then cleaned the amp sleeve which came up very well - almost new looking in fact.  The back panel had long since lost its screws so I located a pair and it fitted perfectly.  Off the amp went to a tech in Athlone, apart from knowing it needed a pair of output valves, I hoped it did not need major surgery.

With the new valves fitted, the amp worked!  The only problem the tech found was that the bass pot was open circuit.  He temporarily fitted a replacement which proved his diagnosis.  He opened up the pot and found the wiper was not making proper contact.  A slight adjustment fixed the pot which was replaced thus keeping the amp almost 100% original.  There is a slight crackly sound when moving the bass control but this is nothing serious.  And it sounds great through my Blackstar 1 * 10" cabinet, which the head almost matches width wise. My wife thinks the pair look very well together.

My music teacher thinks those amps sell for 'silly money' on eBay.  Perhaps they do but I don't see myself ever selling this 1970s gem.  No master volume control, not high gain, just a classic vintage sound, typical of non master volume amps.  I bought the Blackstar cab to go with my Orange Micro Terror.  The Nolan amp is in a different league however, my friend who gave me the amp is calling one of these nights to give it a spin again.

I have not taken any pics yet but can do if anyone is interested.  Amp cabs tend to look similar to one another so maybe there is no need for pics.  Same with sound clips, all that this would show is just how poor a guitar player I actually am.

But it is great to hear this head speaking again after all those years.

photek

Not sure this should be in the classifieds dude?

Rocker

photek said:

Not sure this should be in the classifieds dude?

Thanks mate. Fixed.

photek

Cool story by the way. Pics are always a nice addition!

ICBM

I'm amazed the filter caps are still OK after that amount of time unused!

I think I've seen one of these amps, a long time ago. I don't remember a lot about it, other than it did look hand-made - I think 'true point to point', although I might be wrong.

Pics please .

GuyBoden

ICBM said:

I'm amazed the filter caps are still OK after that amount of time unused!

I think I've seen one of these amps, a long time ago. I don't remember a lot about it, other than it did look hand-made - I think 'true point to point', although I might be wrong.

Pics please .

Do old filter capacitors actually blow. I read that the electrolyte evaporates over the capacitor’s lifetime, altering its electrical properties and the capacitor can fail.  If it does fail, pressure builds up in the capacitor, venting a combustible and corrosive gas inside the amp.

ICBM

Yes.

They can also vent a large amount of slightly corrosive fluid as well, and make quite a mess. In some cases they can short and damage other parts of the amp too.

Personally I wouldn't normally leave the original filter caps in a 40+ year old amp that's been in storage for most of that time, and I don't consider replacing them as any loss of originality. They're a maintenance item, it needs to be done sooner or later.

GuyBoden

ICBM said:

Yes.

They can also vent a large amount of slightly corrosive fluid as well, and make quite a mess. In some cases they can short and damage other parts of the amp too.

Personally I wouldn't normally leave the original filter caps in a 40+ year old amp that's been in storage for most of that time, and I don't consider replacing them as any loss of originality. They're a maintenance item, it needs to be done sooner or later.

Thanks for the info, have another wisdom.

Rocker

@ICBM, Which caps need changing? I will post some pics tomorrow or when I get a minute to take a few photos of the insides of the head. Thanks.

ICBM

Rocker said:

@ICBM, Which caps need changing? I will post some pics tomorrow or when I get a minute to take a few photos of the insides of the head. Thanks.

The big ones .

And the one or two (depending on the circuit) in the bias supply. If you want to be thorough, also the cathode bypass caps in the preamp, although they rarely fail outright and many techs prefer to leave them alone if they're not badly out of spec.

The non-electrolytic caps in the signal path shouldn't need changing unless they're leaking DC - common with old paper-in-oil types, but rarer with more modern dielectrics. Usually you'll know about that if the controls are very scratchy when turned, or if one of the power valve sockets consistently runs the valve too hot when the other one is OK.

Rocker

@ICBM I notice that there is considerable noise from the speaker if no guitar is plugged in to the amp. Even a lead with a silent jack at the guitar end is enough to quieten the amp. Do input sockets short if no jack plug is inserted? Possibly a minor problem in that area. Easily fixed??. Thanks.

ICBM

Rocker said:

@ICBM I notice that there is considerable noise from the speaker if no guitar is plugged in to the amp. Even a lead with a silent jack at the guitar end is enough to quieten the amp. Do input sockets short if no jack plug is inserted? Possibly a minor problem in that area. Easily fixed??. Thanks.

Yes, that sounds like a strained or dirty contact in the jack switch - very common on older amps - you're right, it should short the input to ground when no lead is in.

steven70

..

PhilKing

In the early 70's I had one of Pat's Fender style combos.  It was 50w with 2 12's.  It was massively loud and could cut your head off if you had the treble turned up.  In the end I traded it for a white/wheat Fender Tremolux (I wish I had that now!).  The amp never gave me any problems.  We used to sell a few of them at JSG in Bingley.

ICBM

From the schematic that looks like a straight copy of a 50W PA-model JMP Marshall (model 1985), which itself is an evolution of the 5F6-A Bassman. The only significant difference I can see is that it lacks the 47pF suppressor cap across the PI plates. The power output will depend on the PT voltages and the OT impedance ratio, although the difference between 50W and 60W can depend on how you measure it anyway...

pintspiller

@rocker is this the amp you were selling that I was still waiting on the pictures for?

Rocker

pintspiller said:

@rocker is this the amp you were selling that I was still waiting on the pictures for?

Yes my friend. Apologies for the lack of pictures, life got in the way as it always does.

clarkefan

Fabulous back story from the OP, I have endless tours backing Big Tom and Philomena Begley banging around in my head

DJH83004

ICBM said:

From the schematic that looks like a straight copy of a 50W PA-model JMP Marshall (model 1985), which itself is an evolution of the 5F6-A Bassman. The only significant difference I can see is that it lacks the 47pF suppressor cap across the PI plates. The power output will depend on the PT voltages and the OT impedance ratio, although the difference between 50W and 60W can depend on how you measure it anyway...

The tone stack is configured with a slight difference as well in that the treble pot connects to the wiper of the bass pot which is a little unusual, and would tend to make them more interactive.

ICBM

DJH83004 said:

The tone stack is configured with a slight difference as well in that the treble pot connects to the wiper of the bass pot which is a little unusual, and would tend to make them more interactive.

It won’t make any difference, since the bass pot is just wired as a variable resistance. It’s just drawn differently from normal.