Marmac Super 60

[C Upp]

Hi. I just got my hands on an old neglected Marmac Super 60 amplifier from 1974 that I want to try and bring back to life. I’ve been looking for any information I could find but they seem to be pretty unusual and I can’t find much of anything. Built in Ireland is pretty much all I can find. Last owner said he started it up and it made a loud humming noice so he turned it off. It came to me with only the power amp tubes (2xel34) in it and no preamp or PI-tubes. I’ve found one picture from a guy who fixed up one and he had the PI marked as ecc82.

Does anyone have any experience with these amps or maybe even have a schematic for it? That would help a lot. I have never restored an non running amp before. Just recapping and biasing and I feel a bit over my head diving in blind.

Thankful for any info I can get.

[Enzo]

Is it hard wired or does it use a printed circuit board? I suspect teh amp is not very complex and could be serviced without drawings if need be.

[Mick Bailey]

Can you post some pics of the chassis and electronics? A thorough visual inspection is the first call - looking for bulging or leaking electrolytic caps, burnt components, dripping transformers and wiring issues.

[Jazz P Bass]

My advice when dealing with unknowns as this.
Pull the tubes.
Use/ Build a 'lamp limiter'.

[C Upp]

Thanks for the replies. Will try to get some pictures up. No pcb. It’s hand wired on turret board. It’s not a complicated amp. But it never hurts to have a schematic so I can see what voltages I should be looking for. Electrolytics definatly needs replacing. A few resistors look damaged but seem to measure ok. Have to learn resistor color codes a bit better. Fuses in it were as always not the correct values. So I’ll have to order that.
Will definatly build a lamp limiter but it’s hard getting 100w bulbs nowadays so I’ll have to order that as well.

[Jazz P Bass]

"Will definitely build a lamp limiter but it’s hard getting 100w bulbs nowadays so I’ll have to order that as well."
In this instance you simply want to test the amp without tubes installed.
Even with just the preamp tubes in it should not draw more than 50 watts.

[J M Fahey]

Thanks for the replies. Will try to get some pictures up. No pcb. It’s hand wired on turret board. It’s not a complicated amp. But it never hurts to have a schematic so I can see what voltages I should be looking for. Electrolytics definatly needs replacing. A few resistors look damaged but seem to measure ok. Have to learn resistor color codes a bit better. Fuses in it were as always not the correct values. So I’ll have to order that.
Will definatly build a lamp limiter but it’s hard getting 100w bulbs nowadays so I’ll have to order that as well.

Old style ones are gone but what we really need is a piece of tungsten wire inside a glass bvulb, not matter what they call kit.

"Modern" version is a small quartz lamp inside an old style glass bulb and is widely available, because it´s "higher efficiency".

Same thing,
Only check actual rating, typically "75W equivalent" are actually 53W or so.
It´s printed in the box.

Which is enough to test amp without tubes or with preamp tubes only.

For higher power filament lamps, use a 100W or 150W Quartz stick lamp, with the proper clip sockets of course.

[nosaj]

Thanks for the replies. Will try to get some pictures up. No pcb. It’s hand wired on turret board. It’s not a complicated amp. But it never hurts to have a schematic so I can see what voltages I should be looking for. Electrolytics definatly needs replacing. A few resistors look damaged but seem to measure ok. Have to learn resistor color codes a bit better. Fuses in it were as always not the correct values. So I’ll have to order that.
Will definatly build a lamp limiter but it’s hard getting 100w bulbs nowadays so I’ll have to order that as well.

You don't need a 100 watt bulb. I've use 40s for ever. All i need to see is how the brightness goes. If your in the US just got to the home improvement store and an look for rough service bulbs. Or Dollartree . Even Walmart sells bulbs that work.

nosaj

[Enzo]

Rough service bulbs, heat lamps, special decorative bulbs. There are stull plenty of regular incandescents out there.

[g1]

Also 50 & 60 watt automotive halogen bulbs (also used in some speaker protection circuits).

[J M Fahey]

The automotive halogen lamps are 12V; the ones I suggested are same thing but mains voltage rated.
And with standard E27 base, which is handy.

And as cheap and plentiful as dirt, your corner or Dollar store certainly has them.

[C Upp]

Thanks for the replies again. I have an old 60 watt incandescent bulb saved at home. So I just have to get to the store and get some hardware and I'll build the limiter. Still have to order some stuff from tubeampdoctor but here are some pictures. Just ask if you want to see something in perticular.

As you can see the filter caps really need to be replaced before I put power into it. I've went around it and checked most restors and they mostly seem pretty good. I just have 3 physically damaged resistors that you can see in the last picture. The small ones measure 48Kohm and the large one 100Kohm. But that doesn't seem to fit with the colors I'm seeing... That's where a schematic would come in handy. Or pictures of a similar amp.

And that's not my solder job on those resistors. Someones been in here before. Standby switch has been replaced as well. Don't know if that was a previous attempt at getting it going.

[g1]

Did you measure those damaged resistors with one end lifted?
I would have guessed 100ohm for the big one, your reading for the small ones and the yellow 1st band makes me think 47K.

[vintagekiki]

https://www.facebook.com/atomicanalog/photos/?tab=album&album_id=877179665774113
Marmac Super 60 tube amplifier

[C Upp]

I just lifted the leg on the larger resistor and it still measures 100.7K. The underside was damaged as well so I’ll need to replace that one for shure.
i sent a facebook message to the guy who had that picture up and is waiting for a reply. Not too hopeful since it’s from 2017 but you never know. Hard to tell the value from that picture as well. But it doesn’t seem to be the same one as the one in mine.