A particularly interesting 45/100

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It was the one just mentioned by neilkeel that guided me on pricing for mine to be honest. I thought £4K less for a slightly later amp felt sensible.
 

william vogel

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The C1998 also has the self lead style speaker wire which is actually solid magnet wire covered in the colored sleeves just what this amp has. I’m going to guess but maybe the transformer died or someone decided to go EL34 and swapped the transformer. Who knows but the front panel jtm45 and rear panel jmp along with the aluminum block end chassis make it a transitional model. I don’t know enough about that time to say. I’d look for the output transformer bolt holes. I’ll say that it really has no possibility of the C1998 being original. Ken Underwood would be a good source of information here about this amp.
 

neikeel

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The C1998 also has the self lead style speaker wire which is actually solid magnet wire covered in the colored sleeves just what this amp has. I’m going to guess but maybe the transformer died or someone decided to go EL34 and swapped the transformer. Who knows but the front panel jtm45 and rear panel jmp along with the aluminum block end chassis make it a transitional model. I don’t know enough about that time to say. I’d look for the output transformer bolt holes. I’ll say that it really has no possibility of the C1998 being original. Ken Underwood would be a good source of information here about this amp.
As per my message above I am quite familiar with these. The correct OT is Drake 1202-119. 2” stack with 1k7 primary intended for EL34s out of the box. ie first Superleads and first with EL34s. The next iteration was the first steel chassis JTM ‘Black Flag’ models with almost identical build specs, down to the same PT, choke and dual rectifiers. Later in 67 the Drake 1202-132 OT with 2” stack arrived and the steel chassis JMP100 had arrived. Not sure exactly when the Dagnall C1998 arrived (help @TAZIN!!) but I have had two 104** Superleads with steel chassis and JMP front with C1998s which were punched for 2” Drake OT but fitted with the Dagnall and hand drilled. Both with double brass nuts on the OT fixing machine screws with intact lacquer. Both had C1999 choke and both had cooked PTs - figure that one out.
 
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Here are some detailed photos which show the situation clearly
 

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TAZIN

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Not sure exactly when the Dagnall C1998 arrived (help @TAZIN!!) but I have had two 104** Superleads with steel chassis and JMP front with C1998s which were punched for 2” Drake OT but fitted with the Dagnall and hand drilled.

That's a good question which I'll have to look into when I find some time. My initial guess would be around Sept. - Oct. 1967. But I do recall seeing two amps with a C1998 OT along with transitional filtering which comprised of two RS 64uF/450v caps for the mains, four HUNTS 32 + 32uF/350v for the screens, one HUNTS 16uF/500v (top side mounted) for the phase inverter, and a HUNTS 32 + 32uF/350v preamp filter. This filtering scheme would have directly followed the JTM 100 arrangement.

EDIT: The phase inverter filter cap is actually a Plessey 32uF/500v and not a 16uF. Anyhow, these amps seem to date around November 1967.
 
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Ned B

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I have a low number 12XXX series with D7s and A8s for mustards. I wouldn't be surprised if those 104XXs might have predated the the 12s. I believe these early Dagnall amps used carry-over chassis from the Drake era. I find it interesting that the pre-Dagnall chassis had a filter spacer next to the PT months before a filter was placed there.
 

playloud

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While this thread is still alive, I have a Marshall tip for Ray Davies fans:

Get a copy of Johnny Rogan's 'Ray Davies: A Complicated Life'. At 768 pages, it makes an excellent improvised chassis stand! You just need something similarly-sized for the other end (I have had success with 'Bleak House' and 'Infinite Jest'...)
 

neikeel

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Seanxk

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Yes, much messed with. It was originally shared v1 cathode (split that era had the grey RS 0.68uF 250v bypass caps, not mustards).
Interesting that the joints have been touched in.

It almost looks like it wasn't even a SB, judging by what's been replaced, 3 x very clean Mustards and the obvious 500pf's. But did they make a PA 4 hole around this time.
 

neikeel

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I don’t think 4-hole Pa 100
Obvious signs like completely wrong board mounting screws and transformer fixings are revealing too.
 
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Back to SB/10010 Super Bass having later OT, I spotted this on Solodallas which appears to also be the same later C1998 with the amp only 9 serial numbers later. 3999FCA8-ABDC-4C6A-833E-084705D4FC69.jpeg
 

TAZIN

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Back to SB/10010 Super Bass having later OT, I spotted this on Solodallas which appears to also be the same later C1998 with the amp only 9 serial numbers later. View attachment 101786

SB/10019 appears to have a replaced OT. Unlike the Dagnall C1998 with self-leads this OT has PVC coated flying-leads with the secondary wire colors of: Black, Green, Yellow and Brown (Neg.).

On your amp (SB/10010) the Output Selector has the 100V option and the Dagnall C1998 does not feature that tap. You could varify that your OT doesn't possess a 100V secondary tap by performing a turns ratio test.

The only 100w Drake OT's that Marshall used which featured the 100V tap are the 1202-84 and 1202-119 (Secondary wire colors: Green, Yellow, Blue and Orange (Neg.)).
The Drake 1202-132 (Secondary wire colors: Yellow, Green, Gray and Orange (Neg.)), and the Dagnall C1998 (Secondary wire colors: Black, Yellow, Green and Brown (Neg.)) had 4-ohm, 8-ohm, and 16-ohm secondaries.
 


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