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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 15th Nov 2020, 3:46 pm   #1
Trevor P
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Default Heathkit STR1 tape recorder

Hi all,
I have a Heathkit STR1 tape recorder self build kit that I was given for my 21st birthday in 1970. It worked happily for several years but was confined to the loft probably over 35 years ago. Due to Covid and at a loose end I got it down to look at. It did sort of work and after about 1 week of cleaning etc got it playing a tape at roughly the right speed although it probably needs new belts and idler wheels. I thought I would try some of the old tapes and now on switching on it immediately blue the fuse with sparks somewhere around the power supply area. Does anyone know what power supply transformer I need to try as a replacement? All help appreciated.
Thanks
TrevorP
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Old 15th Nov 2020, 3:54 pm   #2
Cobaltblue
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Default Re: Heathkit STR1 tape recorder

There are a few things to check first and some pictures would be useful.

There are some useful circuits in this thread

https://www.vintage-radio.net/forum/....php?p=1177787

Cheers

Mike T
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Old 15th Nov 2020, 4:16 pm   #3
DMcMahon
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Default Re: Heathkit STR1 tape recorder

What fuse blew, the one in the mains plug, the 0.5A fuse (maybe fuse wire) in the mains voltage selector or the 1A fusing the DC supply ?

David
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Old 15th Nov 2020, 4:24 pm   #4
Trevor P
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Default Re: Heathkit STR1 tape recorder

Hi again,
Initially it tripped the whole power supply too my garage. Did a bit of experimenting for loose wiring etc today and on trying again it blew the small fuse actually on the transformer as well as the trip on the garage supply.
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Old 15th Nov 2020, 4:28 pm   #5
DMcMahon
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Default Re: Heathkit STR1 tape recorder

Suggest first do a good visual inspection (especially the power supply area) looking for any burnt, overheated or leaking components. Always allow at east 15 minutes after switching off (and disconnecting the mains plug from the wall) to expire before doing any internal inspections to allow the capacitors to fully discharge.

Are you experienced in electronics fault finding, do you have any test equipment ?

David
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Old 15th Nov 2020, 9:24 pm   #6
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Default Re: Heathkit STR1 tape recorder

If nothing visually found wrong, then I first recommend to check live and neutral for good isolation resistance wrt (with respect to) ground/earth (with mains switch switched on at the unit).

Also check for no short between live and neutral, there will be a lowish resistance due to the motor connection.

If OK then check for no shorts/low resistance from either of the yellow connections at the mains transformer secondary output winding to earth.

If OK then disconnect the 2 yellow connections at the mains transformer secondary output winding and power up to see if the fuse/trip blows/trips.

If OK reconnect the 2 yellow connections (switch off and isolate the mains first), then remove the 1A fuse. Check both sides of the 1A fuse holder for shorts/low resistance to earth, there will be some resistance reading on the output side of the fuse due to capacitors and other circuit loading.

If OK then power up and measure the DC voltage into the input side of the 1A fuse holder, should be at least +24V. Note - after switching off, the 6,000uF reservoir capacitor C400 will take an extra long time to discharge as there is no circuit loading on it.

Only do the above if you are competent and confident with electrics.

David
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Old 22nd Nov 2020, 11:43 am   #7
Chris55000
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Default Re: Heathkit STR1 tape recorder

Hi!

The mains transformer is 20V @ 1.5A plus 6.3V at 0.5A for the meter illumination bulb!

A transformer rated at 9–0–9V at 2A will do fine – you can always rewire the bulb across the whole of the secondary and replace it with a 24V one!

I have scanned all but the last few pages of the full assembly manual and the service sheet for the TD10, both can be downloaded from this Forum!

Chris Williams
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