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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment.

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Old 14th Jun 2019, 2:34 pm   #1
inigoss
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Location: Donostia-San Sebastian, Spain
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Default Dual Betor EF-1

Hi all.

First of all sorry for my English, I'm from Spain. I'm trying to repair an old record player i found at my father' house which I thought had been thrown away long time ago. Parts from the platter were bent, washers missing, etc. but now it works fine. Problem is the amplifier plate where there is one transformer missing and I only get sound from the right channel. Something else must be wrong because I hear a lot of hum noise, transistors maybe? I don't know too much about electronics, some parts I don't know what they are. In case there is no possibility to fix the amplifier my idea is to replace it with a Chinese one connecting it to the preamp so I can use the volume and tone controls, but no idea how much volts do i need to feed the preamp (with 9 volts from a battery to green and blue wires and grey wire connected to a line input of an old radio I get good sound). I hope you can help me sort this out.

Thank you.
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Old 14th Jun 2019, 5:05 pm   #2
Herald1360
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Default Re: Dual Betor EF-1

Information here:



https://www.radiomuseum.org/r/induct..._mark_211.html


may help. At any rate the output transistors look to be the same and it's unlikely that Bettor would reinvent the wheel for each model.....


The main rail voltage is 28V but it looks like the preamp supply is around 7-8V so your 9V should be fine.

What type of pickup cartridge does yours have- the information I found is for a model with a ceramic type but the preamp setup in yours looks a bit more complex?

A quick Google suggests that perhaps "ben" in this forum has at least had some incidental connection with one of these in a Spanish forum!
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Last edited by Herald1360; 14th Jun 2019 at 5:13 pm.
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Old 15th Jun 2019, 10:55 am   #3
inigoss
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Default Re: Dual Betor EF-1

Thanks for the info. Mine shares amplifier with the TS-20. Cartridge is crystal CDS 630. Transistors are AD 142. Easy to find them.Problem is one transformer missing and some parts i dont know what they are and how to measure them. With the multimeter in DC i get no volts reading at the output of the amp to the preamp(green and blue wires). Gray and blue=14.4v
gray and red=60v
gray and yellow=37v
red and yellow=22v
...
above readings are in case i decide to fit new amp with original preamp so you can help me decide which wires i can use to power them. Thank you!!
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Old 17th Jun 2019, 6:48 pm   #4
inigoss
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Default Re: Dual Betor EF-1

Quote:
Originally Posted by Herald1360 View Post
Information here:



https://www.radiomuseum.org/r/induct..._mark_211.html


may help. At any rate the output transistors look to be the same and it's unlikely that Bettor would reinvent the wheel for each model.....


The main rail voltage is 28V but it looks like the preamp supply is around 7-8V so your 9V should be fine.

What type of pickup cartridge does yours have- the information I found is for a model with a ceramic type but the preamp setup in yours looks a bit more complex?

A quick Google suggests that perhaps "ben" in this forum has at least had some incidental connection with one of these in a Spanish forum!
Hi, where did you get the info about the preamp supply? Is there any transformer that I could use for both the new amp (12-26v DC) and the preamp? Thank you
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