Thank you Stefan for taking on this project and sharing it with us. I have never seen a TO-3 collector connection done that way, but I suppose my Weller 8200 (140 watt) soldering gun could do it 😮 I am not sure why anyone would want to do it that way though! Looking forward to part 2. Regards, David
There are two types of magnetic phono cartridge. Moving coil and moving magnet. The more expensive ones are moving coil. The coil has much lower mass than the magnet so it can be moved faster I guess, for better performance. The output of moving coil cartridges is much lower, so the phono preamp gain must be increased. That is what the switch does. This amplifier would not have been designed to work with a ceramic pickup.
I admit that i´m not so familiar with these topic! MM and MC means moving magnet/moving coil!? Indeed this switch only increases the gain by adding a parallel electrolytic to the emitter resistor of the first transistor. It does NOT change the frequency response - only the gain. I´ll check it in part 3.
Hi Stefan, As well as amateur radio, I’m also really into audio. I owned one of these horrors (mine was the A100 not the X version) back in the late 80’s and blew my student grant to buy it. My suggestion is to kill it with a machete and put it out of its misery, loathsome thing. Mine was unstable in that when someone switched a light on in the house and I was listening to the turntable input it would go into self-oscillation. Then one of the output transistors failed and destroyed one of my speakers. It spent a LOT of time with Musical Fidelity being repaired and didn’t have a good reputation for reliability. I didn’t take mine apart. Why the hell did they do that horrible job on the output transistors? My experience completely put me off Musical Fidelity equipment and that is the only transistor amplifier I’ve ever had an issue with. I get the impression that it operated within an inch of its life and did get extremely hot. Mine used to double as a room heater. The MM/MC is used to switch between moving magnet and moving coil phono cartridge. The capacitor manufacturer is no longer in business - I tried to get some replacements for another project. I’m not normally a negative person, but I was glad to get rid of it.
@@dl7majstefan753 :) Percussive maintenance! I'm not sure. The amp spent a lot of time at Musical Fidelity where they tried to resolve the problem and then it went in to replace the transistors. It was under warranty at the time. Looking forward to part 3! 73 de M0SNR
Thank you Stefan for taking on this project and sharing it with us. I have never seen a TO-3 collector connection done that way, but I suppose my Weller 8200 (140 watt) soldering gun could do it 😮 I am not sure why anyone would want to do it that way though! Looking forward to part 2. Regards, David
We learn something every day.... Yes, a big weller with 100W is OK
Haha. You had me at "That's not nice!" LOLOL! If only this amplifier could talk, what stories it would tell.
Yes - the history would be interesting. The owner doesn´t know details - or he doesn´t want to tell...hi.
That toroidal transformer looks useful for another project. Actually will be interesting following with you on the repair.
Thought the same about the transformer ...
That is a weird way of connecting transistors 😊 those are ‘boutique’ devices, so anything is possible 😂
We learn something every day....
vielen Dank, Stefan. Most entertaining as always. Strange amp though.
Thanks! 😃
what kind of monster connects the collectors like that?
A genius, not a monster!
There are two types of magnetic phono cartridge. Moving coil and moving magnet. The more expensive ones are moving coil. The coil has much lower mass than the magnet so it can be moved faster I guess, for better performance. The output of moving coil cartridges is much lower, so the phono preamp gain must be increased. That is what the switch does.
This amplifier would not have been designed to work with a ceramic pickup.
I admit that i´m not so familiar with these topic! MM and MC means moving magnet/moving coil!? Indeed this switch only increases the gain by adding a parallel electrolytic to the emitter resistor of the first transistor. It does NOT change the frequency response - only the gain. I´ll check it in part 3.
Hi Stefan,
As well as amateur radio, I’m also really into audio. I owned one of these horrors (mine was the A100 not the X version) back in the late 80’s and blew my student grant to buy it.
My suggestion is to kill it with a machete and put it out of its misery, loathsome thing.
Mine was unstable in that when someone switched a light on in the house and I was listening to the turntable input it would go into self-oscillation. Then one of the output transistors failed and destroyed one of my speakers. It spent a LOT of time with Musical Fidelity being repaired and didn’t have a good reputation for reliability.
I didn’t take mine apart. Why the hell did they do that horrible job on the output transistors? My experience completely put me off Musical Fidelity equipment and that is the only transistor amplifier I’ve ever had an issue with. I get the impression that it operated within an inch of its life and did get extremely hot. Mine used to double as a room heater.
The MM/MC is used to switch between moving magnet and moving coil phono cartridge. The capacitor manufacturer is no longer in business - I tried to get some replacements for another project.
I’m not normally a negative person, but I was glad to get rid of it.
My last option is a sledge hammer (would be shown in part 3). Maybe you had instabilities due to bad caps (motor boating) which killed the speaker.
@@dl7majstefan753 :) Percussive maintenance! I'm not sure. The amp spent a lot of time at Musical Fidelity where they tried to resolve the problem and then it went in to replace the transistors. It was under warranty at the time.
Looking forward to part 3!
73 de M0SNR
Sounds like Musical Fidelity should be renamed "Fusable Malady". 73 OM@@rjy8960
It looked a nice amp from the outside but inside looks cheap with the wire soldered to the transistors and wire trapped behind volume pot....
Yes! Tnx