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Discussion in 'Building the Classics' started by bigyinuk, Dec 14, 2017.
Here's a few pictures to start with
Damn, that looks like fun. I've been thinking more and more about a kit. Good luck with the build!
Jealous man. All I have is a box of resistors and caps from Mouser. Some sockets. Everything else seems to be coming via a slow boat from china.
That's one huge Dagnall power transformer!
I've finished it now - (almost) as its missing a couple of resistors due to some confusion about values. Probably get that sorted in the next day or two, then its testing...... Will post more pics and maybe a sound clip.
Looks great! Is that a kit or are you doing it all from scratch?
No, its a kit of parts from Modulus Amplification.
Wow, nice kit looks really high QC and all. Maybe I'll check into those kit builds some time. Are you going to get a cab from Mojtone Tone or somewhere else?
Modulus are supplying the headshell
So cool! I want to do a kit build so bad. Yours looks nice!
Oh dear...... Faulty output transformer - A short circuit on one of the primary windings. Am now waiting on a replacement before I finally get to hear how good she sounds.
Did they give you any crap about replacing it??
Absolutely none, there's one arriving tomorrow with the headshell.
Thats great customer service!! Do they provide good step by step instructions?
Not as such. Michael supplied a board layout schematic to work to and we'd had some prior discussions as to the best order in which to do things. Absolutely everything needed was supplied, all electronic components, valves, screws, wires, brackets, heatshrink etc.
Circuit diagram wise, its the Marshall one which I grabbed from mhuss.com.
Once the amp is working properly (tomorrow fingers crossed) and I've made sure its as noise free as possible, I'll add the effect loop, which is a kit from Tube Town, basically a copy of the Metropoulos one.
The transformer failure is disappointing as I always though Dagnall was a super high quality manufacturer. Michael has had a 1pc failure rate with Dagnall transformers which is, I suppose, low but a b***er if its your transformer. But as you say you can't be too critical as the replacement is arriving so quickly.
BTW the circuit is the cascaded input version which isn't faithful to the original 2204, although the cascaded input *was* present on the 2203. The original 2204s were always criticised for sounding thin at lower drive settings and the JCM800 2204 was modified to include the cascaded inputs. So, although not a 100% 2204 replica, probably a better sounding amplifier.
Love the cascade mod...had it on my jmp 1987. Glad you found the bad part, I would've been pulling my hair out thinking I did something wrong. Keeping my fingers crossed for ya!! Can't wait to see and hear the finished product.
I did for quite a while think it must be my wiring at fault. But the fact that all the DC voltages were correct and there was sound (be it very quiet) led me to look elsewhere in the end. Got the multimeter out and thought "Nah, that's not right" !
Part and cabinet arriving today - excited.
The poor 2204 only lasted a few months (1976 into 1977) the 100w were not blighted at all.