A possibly pointless one but I enjoyed doing it and it shows the wonders of Chinese Ebay!
I have a cousin who tends to collect junk from the 60s. She had a Steepletone portable record player which was no longer working and various electronic repair shops had said it couldn't be fixed so I decided to have a look.
I am actually qualified in electronic engineering but hadn't worked on anything like this in a very long time so was a bit rusty.
I found the turntable was working fine but no sound. Further investigation revealed a knackered transistor on the amplifier board. Simple - buy a replacement transistor. Except they're PNP and I couldn't seem to find a match. Somebody on Ebay in Sweden had NOS but at an extortionate price. There was also a question of what caused it to melt in the first place.
I decided to replace the amp with something else so had a look but a lot seemed expensive and overkill for a very basic record player.
I discovered I could order bare PCB amps with no casings etc from China for a few quid and decided to give that a go. I didn't examine it that closely but it appears the motor for the turntable works of mains voltage with a centre tap transformer providing a c16V AC supply to the original circuit board which had a simple half-wave rectifier on one corner which powered the original amplifier.
I was going to build a bridge rectifier and regulator circuit myself to feed the new amplifier with it's preferred diet of 12VDC. Then I realised I could buy them already made up with China for 99p so their seemed little point in building one myself.
The amp and the rectifier finally arrived on Friday so I put it together this morning. I cut the wires from the tone arm and soldered them on to the lead for the amplifier input and connected the AC feed from the centre tap transformer to the new power supply and then the power supply output to the amp input.
I connected the amplifier output to the speaker. I knew my new amp had a higher rated output than original would have had and I had hoped to replace the speaker with one of the many car speakers I have lying around as it would sound better (so it proved on the "testbench" aka coffee table) but they were too big to fit the casing.
It all worked fine so I started to put it together properly. I used the chassis that the original board mounted on as it seemed easiest and would also locate the volume knob in the correct place. I just had to drill a few holes to facilitate mounting a much smaller PCB.
The casing is wooden and quite thick so the new PCB mounted volume control wouldn't quite reach but with some bodging I was able to use the original volume knob so all looks standard from the outside. The original tone knob and pot is still there but now not connected to anything.
None of this was very challenging but I'm quite pleased with the outcome and I've fixed something that the experts said couldn't be fixed and the parts cost me less than a tenner. It's a bit pointless in some ways as much better turntables can be got, even cheap old hi-fis from car boot sales would sound better than this ever will but it's a nice period piece I guess if you like that sort of thing and has authentic tinny 60s sound. I might try and find a decent speaker to fit the case.
It does have a stereo cartridge but is a mono machine. My new amplifier is stereo only using one channel. Oddly enough it was cheaper to order a stereo amp than a mono one.
I have a cousin who tends to collect junk from the 60s. She had a Steepletone portable record player which was no longer working and various electronic repair shops had said it couldn't be fixed so I decided to have a look.
I am actually qualified in electronic engineering but hadn't worked on anything like this in a very long time so was a bit rusty.
I found the turntable was working fine but no sound. Further investigation revealed a knackered transistor on the amplifier board. Simple - buy a replacement transistor. Except they're PNP and I couldn't seem to find a match. Somebody on Ebay in Sweden had NOS but at an extortionate price. There was also a question of what caused it to melt in the first place.
I decided to replace the amp with something else so had a look but a lot seemed expensive and overkill for a very basic record player.
I discovered I could order bare PCB amps with no casings etc from China for a few quid and decided to give that a go. I didn't examine it that closely but it appears the motor for the turntable works of mains voltage with a centre tap transformer providing a c16V AC supply to the original circuit board which had a simple half-wave rectifier on one corner which powered the original amplifier.
I was going to build a bridge rectifier and regulator circuit myself to feed the new amplifier with it's preferred diet of 12VDC. Then I realised I could buy them already made up with China for 99p so their seemed little point in building one myself.
The amp and the rectifier finally arrived on Friday so I put it together this morning. I cut the wires from the tone arm and soldered them on to the lead for the amplifier input and connected the AC feed from the centre tap transformer to the new power supply and then the power supply output to the amp input.
I connected the amplifier output to the speaker. I knew my new amp had a higher rated output than original would have had and I had hoped to replace the speaker with one of the many car speakers I have lying around as it would sound better (so it proved on the "testbench" aka coffee table) but they were too big to fit the casing.
It all worked fine so I started to put it together properly. I used the chassis that the original board mounted on as it seemed easiest and would also locate the volume knob in the correct place. I just had to drill a few holes to facilitate mounting a much smaller PCB.
The casing is wooden and quite thick so the new PCB mounted volume control wouldn't quite reach but with some bodging I was able to use the original volume knob so all looks standard from the outside. The original tone knob and pot is still there but now not connected to anything.
None of this was very challenging but I'm quite pleased with the outcome and I've fixed something that the experts said couldn't be fixed and the parts cost me less than a tenner. It's a bit pointless in some ways as much better turntables can be got, even cheap old hi-fis from car boot sales would sound better than this ever will but it's a nice period piece I guess if you like that sort of thing and has authentic tinny 60s sound. I might try and find a decent speaker to fit the case.
It does have a stereo cartridge but is a mono machine. My new amplifier is stereo only using one channel. Oddly enough it was cheaper to order a stereo amp than a mono one.
