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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 7th Aug 2017, 8:14 am   #1
jascha
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Cool Cipher Valve tape recorder O.T wax melting -overheating problem

Hi,
I have a Japanese valve tape recorder that for years I have always remembered that it runs hot. I happen to have other identical machines but to my knowledge they run a bit cooler.
I did some work on it and at first had to change a cathode bypass cap (30uf/6v) which measured a staggering esr of 55ohms! Long gone!
The machine uses the following valves: 6AV6, 12AX7, 6AR5 & a 5MK9 rectifier. According to data the 6AR5 should measure a maximum PD of 8.5W! I was not surprised to measure a PD of 9.38W resulting in the OT to melt some of its wax around the chassis! Pictures attached!
I measured all resistors which seemed mostly fine however I did not have a facility to test my valves where I was. The machine is currently in Malta where the mains voltage is 237v. Could it have been my mistake in my younger days perhaps that I had set the primary windings voltage selector to 220v instead of 240v? I was quite pleased to spot that error and when I retested and measured the plate dissipation on the 6AR5 valve it happily measured a lower value of 8.36W . The Anode voltage dropped from 257v to 249v!

The machine seems to run slightly cooler but perhaps still on the hot side compared to its siblings. ( I have 5 of them)! My only question is whether it made any difference substituting a 12AX7 to an ECC83. Could the OT be slightly off considering some of the wax had melted? Any advice is mostly welcome please. I will have the opportunity to test the machine in few months time when I go back there. Should I test with a different set of valves? Different OT?
I practically would like it to run a bit cooler please.

Finally, where can I find a 4 pin connector as seen in the picture please? The plug is fine however the socket that mounts on the chassis has 2 solder pins that snapped off.

Many thanks
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Old 7th Aug 2017, 11:51 am   #2
greenstar
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Default Re: Cipher Valve tape recorder O.T wax melting -overheating problem

jascha, it's hard to tell from the pictures, but the connector looks like a standard B4 valve base type - if it is, replacement of the socket will be fairly easy - is this the case?
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Old 7th Aug 2017, 3:30 pm   #3
jascha
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Default Re: Cipher Valve tape recorder O.T wax melting -overheating problem

Hi, I'm not sure to be honest. I have a couple more pictures I can upload. I will try and get some dimensions some time soon and update
Cheers
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Old 7th Aug 2017, 4:04 pm   #4
Restoration73
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Default Re: Cipher Valve tape recorder O.T wax melting -overheating problem

It's not a B4, but a specific type pattern for 4,5,and 6 pins, and used by Akai and others.
The closest would be the old 6 pin Bulgin, but this is the wrong way round for you:
https://www.cricklewoodelectronics.com/BMCP6.html

I would tend to seek an old 4,5,or 6 pin socket and salvage the connection.
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Old 7th Aug 2017, 7:27 pm   #5
jascha
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Default Re: Cipher Valve tape recorder O.T wax melting -overheating problem

Could it be a Leslie amphenol plug/socket as used in Hammond organs? Just did some research online and am getting close I guess. But where would I find such a socket? I am banking on the Audiojumble fair in October
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