Abbey Harmonic II

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Timoes
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Abbey Harmonic II

Post by Timoes »

Picked up this Abbey. Looks like a well put together 6L6 50 ish watt thing. But the size of the transformers sort of make me think its possibly more. Has got 2 of the power tubes un-used so possibly may have originally been set up for a 100 watts. Single 12 inch "Red Back" speaker. 2 channel with Harmonic switch which pushes it fairly hard into near metal territory. Nice clean too. I did read that the builder, Ross Nicholl, a former tech at Holden, also built a Mesa copy so could be the fore-runner of that. The previous owner told me Ross gave it to him before he packed up and went to Aussie to become a squilloonaire. Its was one of 2 prototypes built for the Sydney guitar show in 1980 apparently. Came in its own Abbey road case too. Neat little bit of NZ amp History. Post up a pic or 2 later if any one us keen for a gawk.
Last edited by Timoes on Sun Jan 22, 2017 3:03 pm, edited 1 time in total.
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Re: Abbey Harminic II

Post by Kris »

pics! a mate has a 60w abbey head similar that was refurbed by steve@baja down here, thing is pretty monstrous.

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Re: Abbey Harminic II

Post by Timoes »

Steve does some good work. Owned a Holden 100 that he had done some work on once also. But this Abbey is also a monster. Pretty cool with the serial # xxx.


Abbey 1.jpg
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Re: Abbey Harmonic II

Post by Ears »

I think these amps were modified from a Vox cct, at least the preamp may have been.

Ross Nicholl's so called "mesa copy" was the Abbey Boogie. It wasn't modelled on Mesa Mk1 except for the styling (cane speaker grill, open back, 112 etc). Had a OD set up quite different to Mesa and an EQ defeat switch which hugely saturated the preamp. Otherwise it was a channel switching master- vol amp with very standard Fender-style power amp section and reverb. Ross used hand wound transformers and it was a high quality hand built amp. Mine (number 70 something) got stolen in '86.
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Re: Abbey Harmonic II

Post by Timoes »

Cool ! It is a Beast of a thing. Hooked it onto a 1960 Cab the other day. Great fun.
Cheers Ears ! ;-)
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Re: Abbey Harmonic II

Post by GrantB »

Nice to see you Ears, posting.

A friend has an Abbey AC30 - apparently it is a fabulous beast. I've yet to hear.
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Re: Abbey Harmonic II

Post by Lawrence »

I had a couple of the Abbey 30s, a harmonic, and a great beast one-off that had a Voxish preamp on a 100 watt marshall esq power section....all great. I used the 100 watt with a Les Paul custom and a switch that swapped the speaker over to a leslie....crazy days. The Abbey 30s I ran full tit with a MXR 6 band graphic in front pushing +10 or so dB at 800 Hz....wow!
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Re: Abbey Harmonic II

Post by jimmy74 »

hi just wondering if anyone has the schematic for the abbey harmonic II or at least any good clear photos of the circuit boards?

thanks

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Re: Abbey Harmonic II

Post by jimmy74 »

I think the problem in this amp is the bias section.... it came to me heavily modified both in the mains filter section and the bias, I've tried to revert as much as I could to 'original specs' but the bias is still very low for this sort of circuit...was getting 23mA idle. So my first question is what should the bias section look like?

thanks

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Re: Abbey Harmonic II

Post by vinylguy »

Is that another valve socket besides the 6L6s ? Was it originally valve rectified ? Probably a good idea to get a tech to give it a good going over. Whereabouts are you ?

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Re: Abbey Harmonic II

Post by vinylguy »

Cool looking amp btw: how come I never come across these deals ??

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Re: Abbey Harmonic II

Post by jimmy74 »

I’ve drawn up a schematic of the current bias circuit with the voltage readings I’m getting. So basically for sovtek 5881 tubes b+ is around 435vdc and bias is -49.7vdc. Obviously power tubes were not installed during testing. The amp is not the one in the photos but exactly the same model. And no I doubt it was ever valve rectified, there are 2 big cutouts in the chassis but my guess is that they were for can caps at one stage. This amp is very noisy and makes loud pops when turning on and off.

Thanks

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Re: Abbey Harmonic II

Post by jimmy74 »

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Re: Abbey Harmonic II

Post by RectifiedAmps »

You have to have the power tubes installed to measure the bias properly. Was it 435vdc without them installed? 23mA at 435v gives you 10W idle, which is 40% of max for sovtek 5881s I think. If you want to run it hotter, the 22k to ground resistor in your bias schematic is the one to reduce to bring up the dissipation.

By noisy, do you mean hum/buzz or hiss? Not sure about Abbeys, but some Holdens and Jansens have terrible grounding designs that create hum.

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Re: Abbey Harmonic II

Post by jimmy74 »

Yes all measurements are done without the power valves in because it is noisy and pops a lot when turning standby on and off (tried installing an x2 cap on the standby switch but that didn’t do much). So which 22k resistor would I have to change?
I’ve also uploaded a drawn up schematic of the HV supply

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