Radiomobile type A & 4100 - UK Vintage Radio Repair and Restoration Discussion Forum

60 oldjohn · 13th Jan 2020, 2:12 pm

The Radiomobile "type A" and 4100 were brought in for repair, can anyone confirm they are a pair? as there is no evidence of them ever working in recent times. Also anyone know where I can get the service sheets?

John

'LIVEWIRE?' · 13th Jan 2020, 2:51 pm

It's a long time since I've seen either the type 'A' amplifier or the 4100 head unit John, but, AFAIK, they can certainly be used together, provided that the connectors are pin-compatible. Both will be valve-based, and produced around the same time, probably mid to late 1950s or very early 1960s. Somewhere in my 'archives' I may have some service info for either or both. The nearest model in Paul's Service Data Lists is the 4200, which is probably very similar.

ajgriff · 13th Jan 2020, 5:09 pm

The 4100 dates from between 1951 and 1955. The A-Type amplifier was one of the power unit options. Radiomuseum has some information.

Alan

Hartley118 · 13th Jan 2020, 5:32 pm

AFAIK those two units are a pair..

The type A amplifier is the single-ended power amp. You should find this valve line up: W77, DH77, N78.

Somewhat idiosyncratically, the signal that links the head unit to the amplifier is at IF frequency. It travels in that screened multicore cable along with audio to and from the volume control and the 12V power switching. I've found that multicore cable very vulnerable to breaks. If that's the case, I've found a reliable solution is to replace it with several smaller 4-way cables.

I have circuits and service data, but don't have evidence of where I sourced them from and, after the recent unhappy event, I don't want to risk rustication by publishing them on the forum.

Moderators: what's the correct procedure here please?

Interestingly, I've normally found the paper capacitors in these units to be in decent shape, so it's worth checking before any wholesale replacement.

Best of luck John - when working to spec, these are remarkably sensitive receivers, though bench testing can be problematic due to interference from the vibrator supply.

Martin

ajgriff · 13th Jan 2020, 5:39 pm

Quote from Forum Rule F4:

"Discussion of motor vehicles is prohibited, but discussion of radio, audio and associated equipment and electric clocks fitted to vehicles is allowed."

You appear to be on safe ground as far as I can see.

Alan

MotorBikeLes · 13th Jan 2020, 6:48 pm

I think that amp unit contains a non-synchronous vibrator.
I had one, but it may have been a bigger one. Back in 1967 I owned a Healy Abbot DHC, fitted with the radiomobile dashboard unit, and the amp under the bonnet. Two speakers, one in each door. i am fairly sure mine had a dual output (EL41s maybe?). I seem to recall it was longer than your Type A.
I remember trying to get the vibrator to run reliably (gentle filing), but not very sucsessful, so I bought a new replacement. It had a load of black caps, can't recall the make, and the distorted output became acceptable once they were replaced. A long time ago.
Les.

barrymagrec · 13th Jan 2020, 7:02 pm

I have seen two of these amplifier units, one in an R type Bentley, both had a pair of N78s as the output valves and a Plessey 1214 vibrator.

I think the head unit in the Bentley was more involved than this one appears to be.

My understanding was that the connecting lead was tuned for the IF and so the radio would only operate with the length of lead it had been set up for.

60 oldjohn · 13th Jan 2020, 8:03 pm

Thank you all for the replies. Martin, I have sent an Email, it could have gone into the junk mail if you can not find it.

John.

AC/HL · 13th Jan 2020, 9:20 pm

Quote:

Originally Posted by Hartley118

Moderators: what's the correct procedure here please?

If it's not in VRSD, and in the public domain, there is no problem posting as far as we're concerned. If it was acquired on the understanding that it was not published, that's a matter for the poster. Radiomuseum are one such source, and they take a dim view of watermarked documentation appearing here. If in doubt, just post the minimum required to illustrate a problem.

MotorBikeLes · 13th Jan 2020, 11:05 pm

BarryMgee, YES, they were N78s in my amp. From your comments, it is safe to conclude there WERE two amps. mine in the Healy obviously similar to the one in the Bently. The higher spec model.
Les.

ajgriff · 13th Jan 2020, 11:22 pm

I think the 4200 was the upmarket model with five pre-set buttons rather than three plus improved sensitivity.

Alan

13th Jan 2020, 2:12 pm	#1
60 oldjohn Dekatron Join Date: Dec 2004 Location: East Yorkshire, UK. Posts: 3,988	Radiomobile type A & 4100 The Radiomobile "type A" and 4100 were brought in for repair, can anyone confirm they are a pair? as there is no evidence of them ever working in recent times. Also anyone know where I can get the service sheets? John Attached Thumbnails __________________ My favourite text message "I'll be there in five minutes, if not read again"

13th Jan 2020, 2:51 pm	#2
'LIVEWIRE?' Rest in Peace Join Date: Mar 2006 Location: N.W. Oxfordshire(Chipping Norton) Posts: 7,306	Re: Radiomobile type A & 4100 It's a long time since I've seen either the type 'A' amplifier or the 4100 head unit John, but, AFAIK, they can certainly be used together, provided that the connectors are pin-compatible. Both will be valve-based, and produced around the same time, probably mid to late 1950s or very early 1960s. Somewhere in my 'archives' I may have some service info for either or both. The nearest model in Paul's Service Data Lists is the 4200, which is probably very similar. Last edited by 'LIVEWIRE?'; 13th Jan 2020 at 2:56 pm.

13th Jan 2020, 5:09 pm	#3
ajgriff Nonode Join Date: May 2004 Location: Halifax, West Yorkshire, UK. Posts: 2,587	Re: Radiomobile type A & 4100 The 4100 dates from between 1951 and 1955. The A-Type amplifier was one of the power unit options. Radiomuseum has some information. Alan

13th Jan 2020, 5:32 pm	#4
Hartley118 Nonode Join Date: Aug 2015 Location: Cambridge, Cambs. UK. Posts: 2,198	Re: Radiomobile type A & 4100 AFAIK those two units are a pair.. The type A amplifier is the single-ended power amp. You should find this valve line up: W77, DH77, N78. Somewhat idiosyncratically, the signal that links the head unit to the amplifier is at IF frequency. It travels in that screened multicore cable along with audio to and from the volume control and the 12V power switching. I've found that multicore cable very vulnerable to breaks. If that's the case, I've found a reliable solution is to replace it with several smaller 4-way cables. I have circuits and service data, but don't have evidence of where I sourced them from and, after the recent unhappy event, I don't want to risk rustication by publishing them on the forum. Moderators: what's the correct procedure here please? Interestingly, I've normally found the paper capacitors in these units to be in decent shape, so it's worth checking before any wholesale replacement. Best of luck John - when working to spec, these are remarkably sensitive receivers, though bench testing can be problematic due to interference from the vibrator supply. Martin __________________ BVWS Member

13th Jan 2020, 5:39 pm	#5
ajgriff Nonode Join Date: May 2004 Location: Halifax, West Yorkshire, UK. Posts: 2,587	Re: Radiomobile type A & 4100 Quote from Forum Rule F4: "Discussion of motor vehicles is prohibited, but discussion of radio, audio and associated equipment and electric clocks fitted to vehicles is allowed." You appear to be on safe ground as far as I can see. Alan

13th Jan 2020, 6:48 pm	#6
MotorBikeLes Nonode Join Date: Dec 2012 Location: Kirk Michael, Isle of Man Posts: 2,350	Re: Radiomobile type A & 4100 I think that amp unit contains a non-synchronous vibrator. I had one, but it may have been a bigger one. Back in 1967 I owned a Healy Abbot DHC, fitted with the radiomobile dashboard unit, and the amp under the bonnet. Two speakers, one in each door. i am fairly sure mine had a dual output (EL41s maybe?). I seem to recall it was longer than your Type A. I remember trying to get the vibrator to run reliably (gentle filing), but not very sucsessful, so I bought a new replacement. It had a load of black caps, can't recall the make, and the distorted output became acceptable once they were replaced. A long time ago. Les.

13th Jan 2020, 7:02 pm	#7
barrymagrec Octode Join Date: Dec 2017 Location: Morden, Surrey, UK. Posts: 1,560	Re: Radiomobile type A & 4100 I have seen two of these amplifier units, one in an R type Bentley, both had a pair of N78s as the output valves and a Plessey 1214 vibrator. I think the head unit in the Bentley was more involved than this one appears to be. My understanding was that the connecting lead was tuned for the IF and so the radio would only operate with the length of lead it had been set up for.

13th Jan 2020, 8:03 pm	#8
60 oldjohn Dekatron Join Date: Dec 2004 Location: East Yorkshire, UK. Posts: 3,988	Re: Radiomobile type A & 4100 Thank you all for the replies. Martin, I have sent an Email, it could have gone into the junk mail if you can not find it. John. __________________ My favourite text message "I'll be there in five minutes, if not read again"

13th Jan 2020, 11:05 pm	#10
MotorBikeLes Nonode Join Date: Dec 2012 Location: Kirk Michael, Isle of Man Posts: 2,350	Re: Radiomobile type A & 4100 BarryMgee, YES, they were N78s in my amp. From your comments, it is safe to conclude there WERE two amps. mine in the Healy obviously similar to the one in the Bently. The higher spec model. Les.

13th Jan 2020, 11:22 pm	#11
ajgriff Nonode Join Date: May 2004 Location: Halifax, West Yorkshire, UK. Posts: 2,587	Re: Radiomobile type A & 4100 I think the 4200 was the upmarket model with five pre-set buttons rather than three plus improved sensitivity. Alan