Bogan Boutique Amplifiers

10/10/2025

I know, it's been three weeks since I last posted. I always said I'd only post interesting stuff on here, and most of the work I've been doing has been the same stuff that I've already posted on. And nobody wants to see that.

So here's something interesting. A JCM2000 DSL100. With a runaway bias problem. I got this amp in, and the owner reported it had lost signal and was sounding poorly. I put it on the workshop bench and plugged the bias probes in, and one of the tubes started running away. A few tests later and the conclusion was that the board had gone conductive and we needed to replace it.

So a new board was purchased from Brad's Guitar Garage in Australia:
https://www.bradsguitargarage.com.au/fym2000-2-channel-pcb-replacement-assembly-for-mar

and when it arrived it was time to swap it over.

23/09/2025

Heads up folks.

Because of a change in my full-time job (yes, this ain't my main gig) I am having to change my hours of work here, and in the new year the hours I can work on amps are going to have to reduce further as my main work insists on me spending more time in the office.

Sorry about that folks, it is what it is. I'll still be doing work on amps, it'll just take a bit longer. In the meantime I have some nice amps I am working on that I will have some stories up on real soon.

Hope everything is going well in your lives and your amps are happy too.

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16/08/2025

I know, it's been a while. I like to only post about things that I hope you will find interesting, and I have been doing a lot of amps that are the same as ones I've already done, and I'm sure you don't want to read the same old stuff.

So here's something interesting. A Concord Cloud 7. A what? I hear you say. Well, it's from the 1960s, a New Zealand (Auckland) made amp, featuring a pair of EL34s cathode biased for 25watts, going into a Phillips 12UEG alnico guitar speaker. The setup is similar to a Twin Reverb, except no reverb. And that's where the similarities end.

01/06/2025

Okay, buckle up, this is gonna be a long one. I have 39 pics in this set, so bear with me while I load them up and talk about it. It's a 1970 JMP 50w lead, aka the JMP Plexi, made sometime between July 1969 and Dec 1970.

It belongs to the son of a friend who sadly passed a couple of years back now. My friend gifted me my handwired Jansen Bassman 75, and it's lovely to be able to bring this one back for his son, who intends to use it for live performances.

So, I better do a good job on it. It looks pretty original from the front.

26/03/2025

It's been a week for capacitors. This Silver Jubilee 2553 turned up for a service. It's in near original condition, and that means it's using the original LCR caps, which are nearly 40 years old. In order to get it working in as-new condition it needs a recap and a bias in order to be working at its best again.

26/03/2025

This Friedman Runt 20 turned up on my bench lately. Friedmans are high quality amps, and don't tend to have many problems. This one does have an issue though - it's humming like it doesn't know the words, and it's a 100Hz hum, which generally means filter caps. Which is weird, because this amp is relatively new, and they use high quality ARS caps that don't tend to have problems with that. However, I spent some time with the capacitance meter, and two of them were reading way high in the impedance. So it looks like at least two of the capacitors in this amp have failed. Bad form ARS.

19/03/2025

So, this one crossed my bench lately for a repair they all need. The original potentiometers in these amps are hideous and they always crap out. The solution is to replace the original Russian potentiometers with decent pots which will return functionality.

Here's a brief description of the process in case you wondered what has to be done.

17/03/2025

So, this has to be the hardest gigging amp in New Zealand. Fresh off 52 shows in the last 52 weeks with the Bravo Uniform Mikes aka the BUMs, it came here sounding quiet, distorted and farty. I've worked extensively on the amp. I used to own it, and it's had the full treatment. Well, I tracked the problem down, with the help of solid state guru Glen Cowan, to a malfunction in one of the operational amplifier chips. The amp uses multiple FET based op amps in a similar way to valves, and one or more had given up the ghost. Hardly surprising since the amp is nearly 50 years old. With an all new set of U741CPs it's all good to go again. Those 6L6 tubes are lasting well too.

07/03/2025

Unashamed plug for my hard rock band. Mister Unit, playing at Underworld Tavern on 4 April. With So Keen and Spookytones supporting.

Some good old hard rock for the masses. Should be fun.

https://www.facebook.com/events/1169684028191656/?acontext=%7B%22event_action_history%22%3A[%7B%22mechanism%22%3A%22attachment%22%2C%22surface%22%3A%22newsfeed%22%7D]%2C%22ref_notif_type%22%3Anull%7D

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04/03/2025

While I'm on the subject of old amps, here's one that ended up on my bench recently. It's a very very tidy Jansen 6 Twenty, and boy is it lovely. It's come in because one channel wasn't working and the noise floor is a bit high.

I tracked the noise issue down to a power filter cap that was past it's useby date, and the channel dropout was due to a problem with the volume pot.

Easy fixes, but I thought you'd like to see the amp.

04/03/2025

Here's an amp you don't see very often. A late 1967 Marshall JMP-100 #6 model. It's for sale, so if you are interested, it's in the Wellington area and I can get you in touch with the owner. Originally owned by the Golden Horn Sound Company back in the 60s and 70s, it spent many years as the guitar amplifier for Strikemaster. Aside from rebuilt bridge rectifier diodes and a hardwired power cord replacing the original Bulgin power socket, this amp is in original condition.

21/12/2024

I found out something about these DSL40CR amps that Marshall is not telling you, and I thought I'd share.

This amp came in with a huge noise floor - ridiculously loud static in both channels that got louder as you turned the amp up.

I did all the regular tests - checked and replaced all tubes. Tested the plate load resistors and bypass resistors. Checked coupling caps. All good.

Then I found something on the Marshall Forums that some guy in Russia had posted about incorrect components in the resonance circuit.

Resistors R141 and R148, which work with the transistors that amplify the resonance signal are incorrect.

They should be 1Mohm. Instead there are 470k resistors in there, labelled as 1M.