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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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26th Nov 2021, 11:39 pm | #1 |
Diode
Join Date: Aug 2021
Location: Enschede, Netherlands.
Posts: 7
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Quad FM4: small extra pcb?
Hi,
I bought an FM4 a few months ago, and today I had a look inside. The battery seems renewed and put in a plastic box. There seems to be an extra pcb connected to the battery. Any idea what this is? |
27th Nov 2021, 2:45 pm | #2 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,996
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Re: Quad FM4: small extra pcb?
It looks to be in amongst the RF circuitry. Could it be a RF preamplifier??
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27th Nov 2021, 10:34 pm | #3 |
Diode
Join Date: Aug 2021
Location: Enschede, Netherlands.
Posts: 7
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Re: Quad FM4: small extra pcb?
It looks like it’s only mechanically connected to that metal can thing (glue). The wires seem to go to the battery. The FM4 works as specified.
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29th Nov 2021, 12:10 am | #4 |
Heptode
Join Date: Jan 2008
Location: Ashhurst, Manawatu, New Zealand
Posts: 570
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Re: Quad FM4: small extra pcb?
Other pix of the FM4 seem to have a different battery but the same small board next to a couple of transformer cans. A blog says that the battery is for memory backup - the memory is probably that big fat Philips chip.
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29th Nov 2021, 12:16 am | #5 |
Dekatron
Join Date: Nov 2011
Location: Surrey, UK.
Posts: 4,394
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Re: Quad FM4: small extra pcb?
A more sympathetic/sophisticated charging/change-over circuit for the battery?
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29th Nov 2021, 12:26 am | #6 |
Heptode
Join Date: Jan 2008
Location: Ashhurst, Manawatu, New Zealand
Posts: 570
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Re: Quad FM4: small extra pcb?
Here's the schematic of the memory side of things but I don't see a keep-alive battery in there. Perhaps the many references to "Ref H" is not on this schematic actually goes to the battery. Still no idea what the OC board does though.
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29th Nov 2021, 9:08 am | #7 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,535
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Re: Quad FM4: small extra pcb?
That diagram isn't the clearest but the battery is almost exactly in the middle of it, at the bottom left of the group of diodes left of IC5. It's a 4.8V NiCd type.
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29th Nov 2021, 9:21 am | #8 |
Heptode
Join Date: Mar 2017
Location: Romsey, Hampshire, UK.
Posts: 521
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Re: Quad FM4: small extra pcb?
Hi
In the middle of that schematic there is what looks like a battery symbol, labelled 4.8 V B1 |
29th Nov 2021, 10:51 am | #9 | |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,979
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Re: Quad FM4: small extra pcb?
Quote:
An image that shows this is on DADA's site https://shop.dadaelectronics.eu/quad...108461833.html I think when I bought mine (from Quad, not DADA) I recall it was about forty quid. Craig
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29th Nov 2021, 10:57 am | #10 |
Hexode
Join Date: Oct 2019
Location: Weymouth, Dorset, UK.
Posts: 475
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Re: Quad FM4: small extra pcb?
Could it be this;
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29th Nov 2021, 11:51 am | #11 |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,979
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Re: Quad FM4: small extra pcb?
I wondered that, but it seems to be in the wrong part of the board for that, and peering at the OP's photos it just looks like a resistor and a transistor.
It would be helpful if we had more details about what is on that board, and where the wires are connected.
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29th Nov 2021, 8:15 pm | #12 |
Diode
Join Date: Aug 2021
Location: Enschede, Netherlands.
Posts: 7
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Re: Quad FM4: small extra pcb?
Thanks for all replies. The FM4 is already in my small stack again, between the 34 and 306. . What I see from my photo is the add-on pcb contains 4 resistors and 1 transistor.
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