Help needed with Vauxhall Car Radio

[AD360 Rob]

Evening all,

I've been asked to "have a look at" the radio from my friend's Vauxhall Victor 101 (I should point out it was bought for that car and not already fitted) I'm having trouble identifying the manufacturer. Internally it uses the typical transistor line up of 3x AF117, a couple of OC or AC audio jobbies and an AD149 output device. It is reminiscent of Phillips built car radios and indeed I have servicing info for the later (1967) radio which is more sophisticated. I reckon this one is from 1964 - 1966.
The issues I am having with it were threefold. First a horrid squealing which was a dried out Output coupling cap, then no signals which was cured by replacing the AF117s. Now it works fairly well apart from intermittent noise which is NOT volume control dependant so I'm suspecting a transistor or cap in the amp which looks an absolute swine to get to.
Another potential problem is that this radio is positive earth with no visible means of changing polarity unlike most Phillips versions and the later Vauxhall models. My friend's Victor 101 is Negative earth. Can anyone shed any light on a manufacturer and model for this set or info on how to changer the polarity if indeed this is possible?

Cheers chaps

Rob

['LIVEWIRE?']

I'm not sure what make that radio is, Rob. It's a 'made for Vauxhall' one, possibly by Plessey. Can't help with the polarity change I'm afraid, but I'd replace those Red & Yellow Plessey Electrolytic capacitors, regarding them as 'change on sight' devices. The intermittent noise could be caused by bad earths (dry joints or loose earthing screws/tags) The service data is available from 'up top' for £1.99. Look for ' Vauxhall Manual Car Radio' under 'Plessey'

[AD360 Rob]

Aah, I didn't even think about Plessey, I have the DVD so will take a look at it now.
I agree those red and yellow caps will have to go, hateful things and replacing them may even cure the noise.
I'll let you know how I get on.

Cheers
Rob

[kalee20]

Might be easier to change the polarity of the car than the radio! Unless there are any permanent-magnet motors (and even they may be swappable-over) or electronic ignition, it's reverse the battery, repolarise the dynamo, and go...

[AD360 Rob]

Agreed Kalee20, the owner is going to have to do that if he is intent on using this radio as there's no way to change polarity unfortunately.

['LIVEWIRE?']

Surely a Vauxhall Victor 101 would originally have been Positive Earth, dating, as it does, from the early 1960s, so, unless it has been modified, e.g., by having an alternator or electric fuel pump fitted, it should be possible to reconvert it to Positive Earth (N.B. I'm not a motor mechanic, so advice shoulfd be sought from someone familiar with early 60s Vauxhalls before proceeding.)

[electronicskip]

I have a positive to negative converter I used to use on a Ford Anglia many years ago so I am sure they are still about.

[emeritus]

The 3 pin plug looks like the type used by Plessey on the radios they made for Ford in the late 1960's. In the 1970's I worked for a while with one of the engineers who had previously been in the part of Plessey that designed their car radios. He gave me a copy of the circuit diagram of the Ford push-button models that were then being sold off cheaply in the staff sales shop, some of which had been modified for were positive earth, and did explain how to change the the polarity, but I don't recall precise details now. The main mod was fitting mica washers to the power transistors to electrically isolate them from the metal chassis that was used as the heat sink.

[cheerfulcharlie]

Originally Posted by 'LIVEWIRE?'

Surely a Vauxhall Victor 101 would originally have been Positive Earth, dating, as it does, from the early 1960s, so, unless it has been modified, e.g., by having an alternator or electric fuel pump fitted, it should be possible to reconvert it to Positive Earth (N.B. I'm not a motor mechanic, so advice shoulfd be sought from someone familiar with early 60s Vauxhalls before proceeding.)

Yes I agree Fords were switched to Negative Earth from late 65 for the 66 model year.. Vauxhalls around the same time. IIRC both Fords and Vauxhall had a warning sticker under the bonnet to say that they were now Neg Earth (presumably Neg Earth was in anticipation of the introduction of the alternator?)

The clue might be if a clock had been fitted from new as this is obviously polarity critical or a Rev counter (but I think Vauxhall stayed with mechanical drives longer than Fords?)

At one time you could get ABS radio consoles to bolt under the dash and therefore isolate the polarity of the radio.

[Boater Sam]

You can still change most older vehicles over to positive ground, even with alternators.
Use a marine isolated return alternator and a bit of fiddling.

['LIVEWIRE?']

Out of interest I've looked on the 'net for specifications of the Victor 101, and none that I've found states what the original polarity was. However, given that the Plessey radio in the OPs original enquiry is (a) Positive Earth, (b) branded 'Vauxhall', and (c) dates from the right era, I would expect 101s (and other early 60s Vauxhalls) to have been Positive Earth when new.

[Radio Wrangler]

There is no single right answer.

The 101 had a dynamo. Cars of that era, provided no electronics had been added often had their polarity swapped by changing the battery connections and giving the dynamo field terminal a quick flash to reverse the residual magnetism. The usual reason was the fitment of a radio with fixed -ve earth polarity (cheaper then the switchable models). Any permanent magnet motors (wipers, heater) would run backwards and not many people noticed!

So the possibilities are:

1) put the car back to +ve earth (might need a dynamo or a rare alternator)
2) insulate the whole radio from everything and float the casing at 12 live (and expect people to take care not to short)
3) start insulating everything inside the radio so i now works with its +ve rail to chassis.
4) Rebuild the radio with NPN devices, reverse polarised capacitors. Put a big label on the rear!
5) Find another radio a bit later that can do -ve earth

(1) scores max brownie points for the historical vehicle aspect

I'd go for (4) It's a simple set with not a lot in it and it gets round the AF11x business. It keeps things looking original.

Had it been one of the 12v on the anode valve sets, you'd have been looking for complementary valves ;-)

David

(P.S. PM wiper motors running backwards put the thrust at the wrong end of the armature and wear out)

[The Philpott]

I have a slightly later japanese mw/lw radio that has switchable voltage AND switchable polarity. If your friend wanted to give up and change to a different set let me know the dimensions of the 'void' in the dash and i'll dig it out.

Needless to say, broadly speaking any vehicle over 20 years old really wants a battery isolator to mitigate fire/theft risk.

[Synchrodyne]

As I recall - a bit vaguely by now, admittedly - the Vauxhall FC started out with a positive earth electrical system, but was changed to negative earth (maybe with an alternator for some markets) late in the production run - say circa 1967. So the negative earth on the vehicle at interest may well have been original.

Cheers,

['LIVEWIRE?']

There is actually another way to get around the 'wrong polarity' radio, though it would still involve isolating the radio's metalwork from that of the car, and isolating the aerial screening by cutting it somewhere close to the aerial plug then fitting suitable isolating capacitors to maintain AC (signal) earthing. I forget what value caps. should be used, but tthat chosen should provide a low impedance path to earth for any interference picked up by the coaxial cable's screening. Fitting a bridge rectifier in the supply lines to the radio (this was done in a few models by the makers) means it can be powered by a supply of either polarity, although about 1.2v. is lost due to the presence of the (silicon) diodes in the bridge rectifier. Any type with a PIV (VRRM) of 60 or more per diode should be OK, maybe one of the WO series.

[kalee20]

I'd be surprised if either the wipers or the heater blower were permanent magnet motors, TBH! My Morris and Land-Rover used shunt-wound stators, which of course run the same way whatever the polarity. (A sucking heater wouldn't be much good anyway!)

Really, the only reasons NOT to swap the vehicle polarity is if it has been fitted with an alternator, or electronic ignition.

[Station X]

I can certainly remember a heater motor running backwards. I had to reverse the connections to the field winding.

Before speculating any further perhaps we should wait for the OP to advise the vehicle's earth polarity and the possibility of changing it?

[Biggles]

When I used to fit two way radios into vehicles, there was a gadget called an isolating converter which converted 12V to 12V but the output was floating and electrically isolated from the input. They were made by Alfatronix (still in business) and were good quality bits of kit. It may be worth looking into using one of these.

[D Cassidy]

Hello.
The Victor 101 was negative earth from 1966 when they fitted an alternator to the VX4/90 the lower ones (101) were also negative earth at that time, in general those with 4 speed floor change gearboxes had an alternator the cooking version with bench seat and column 3 speed change had a dynamo.
Oddly enough I was looking at a 101 last Sunday a 1965 model and it was negative earth, it may have been changed but the battery leads looked to me as if it was that way from the factory.

[AD360 Rob]

Morning all,

Wow, Thanks chaps I certainly have a number of options there. I'll have a chat with the owner and decide on the way ahead after I have researched some of the options you have all suggested.

I have found the cause of the intermittent audio noise, it's the OC82DM. a quick blast with the freezer spray cures it, heating the case with a finger causes it. Now I just have to work out how to get it out without dismantling the tuning drive.

Most of those Plessey caps seem to check ok for value but their ESR varies from 6 ohms upwards so they will be replaced as a matter of course.