Dual Bettor EF-1 - UK Vintage Radio Repair and Restoration Discussion Forum

inigoss · 14th Jun 2019, 2:34 pm

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.

Herald1360 · 14th Jun 2019, 5:05 pm

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!

inigoss · 15th Jun 2019, 10:55 am

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!!

inigoss · 17th Jun 2019, 6:48 pm

Quote:

Originally Posted by Herald1360

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

ben · 19th Jun 2019, 9:52 pm

Si te falta el transformador de salida, lo mas probable es que han petado dos de los transistores de salida. Yo no me complicaría la vida, y sin esquema, creo que sería mejor meterle un módulo de velleman o de los chinos (TDA 7297 te daría 15w+15w, o sea, parecido a lo que trae).

Para su alimentación, te valdrían los 14v del preamp del bettor (verde y azul) . Otra opcíon sería meter un transformador de 9 o 12v dentro del tocadiscos, habrá espacio en el mueble, situandole dónde no estorbe la mecánica del plato ni provoca interferencias en los señales de audio.
Ya nos contarás,

-----
If the transformer is missing (presumed faulty) then it's probable the output transistors are also bad a a result. I would simply go for a mini amp module kit, especially if you don't have a circuit diagram. Those with TDA 7297 give an o/p of 15w+15w, similar to what it came with originally.

You could power you module with the feed for the preamp (blue and green cables). Or I suppose you could put a wall wart somewhere in the cabinet, situating it where it won't foul the deck mech or cause noise.
Keep us updated,

inigoss · 20th Jun 2019, 7:03 pm

Already ordered a Chinese amp. Green and blue wires are not + and -. If i feed them with a 9v battery only get sound from the channel connected to +.
Green and blue connected to - , and + to preamp output -, then both channels work. I hope i'm not doing anything wrong. Gracias

14th Jun 2019, 2:34 pm	#1
inigoss Retired Dormant Member Join Date: Jun 2019 Location: Donostia-San Sebastian, Spain Posts: 4	Dual Bettor 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. Attached Thumbnails

14th Jun 2019, 5:05 pm	#2
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	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! __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O Last edited by Herald1360; 14th Jun 2019 at 5:13 pm.

15th Jun 2019, 10:55 am	#3
inigoss Retired Dormant Member Join Date: Jun 2019 Location: Donostia-San Sebastian, Spain Posts: 4	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!! Attached Thumbnails

19th Jun 2019, 9:52 pm	#5
ben Dekatron Join Date: Aug 2006 Location: Madrid, Spain / Wirral, UK Posts: 7,498	Re: Dual Betor EF-1 Si te falta el transformador de salida, lo mas probable es que han petado dos de los transistores de salida. Yo no me complicaría la vida, y sin esquema, creo que sería mejor meterle un módulo de velleman o de los chinos (TDA 7297 te daría 15w+15w, o sea, parecido a lo que trae). Para su alimentación, te valdrían los 14v del preamp del bettor (verde y azul) . Otra opcíon sería meter un transformador de 9 o 12v dentro del tocadiscos, habrá espacio en el mueble, situandole dónde no estorbe la mecánica del plato ni provoca interferencias en los señales de audio. Ya nos contarás, ----- If the transformer is missing (presumed faulty) then it's probable the output transistors are also bad a a result. I would simply go for a mini amp module kit, especially if you don't have a circuit diagram. Those with TDA 7297 give an o/p of 15w+15w, similar to what it came with originally. You could power you module with the feed for the preamp (blue and green cables). Or I suppose you could put a wall wart somewhere in the cabinet, situating it where it won't foul the deck mech or cause noise. Keep us updated, __________________ Regards, Ben.

20th Jun 2019, 7:03 pm	#6
inigoss Retired Dormant Member Join Date: Jun 2019 Location: Donostia-San Sebastian, Spain Posts: 4	Re: Dual Betor EF-1 Already ordered a Chinese amp. Green and blue wires are not + and -. If i feed them with a 9v battery only get sound from the channel connected to +. Green and blue connected to - , and + to preamp output -, then both channels work. I hope i'm not doing anything wrong. Gracias