BJ8 Tachometer, "sparking"

[pkmh]

Re: BJ8 Tachometer, "sparking"

Since I am in the "antiquing" biz, I do find from time to time these inverters, although they are a bit bulky and do get plugged into a wall socket, but I will investigate for use in the car. It would be nice once in a while to listen to the radio, but not a priority.

But from the above comments suggesting this radio is a later model, then is it possible the setup may be negative ground instead of positive? What do you all suppose is a giveaway clue this is set up for positive, or negative for that matter? Maybe somebody out there has this same type radio and can comment more on it's spec's?

Another point I should note: This radio was in the car when I bought it, but never been hooked up, so I have no idea as to its polar setup there, either. Maybe I can lucky and find out it is for a negative setup.

BTW, I doubt it makes any difference, but my car is a 1967, though from my discussion with one Healey member, it or most of it was probably made during 1966 (and maybe some other parts of it in 1965, or earlier--who knows).

Maybe from the code numbers inscribed on the radio casing, I might get lucky and find more about it on the internet. If anyone knows from the numbers I've shown which one is referred to as the model number, then please advise on that if you can.

My very last resort to attempt to see if this radio even works, I will have to investigate how to set up for testing (and most likely taken out of the car first) to determine its polar setup.

But thanks for the help!

Very much appreciated.

Paul

 

[Bob_Spidell]

Re: BJ8 Tachometer, "sparking"

...
Maybe from the code numbers inscribed on the radio casing, I might get lucky and find more about it on the internet. If anyone knows from the numbers I've shown which one is referred to as the model number, then please advise on that if you can.
...

I looked through the previous posts and didn't spot any numbers, can you post again?

 

[pkmh]

Re: BJ8 Tachometer, "sparking"

Okay, got the pictures posted here of the radio. There are a few areas with numbers and I highlighted for easier reading. But the bottom part of the radio also has a number inscribed I did not catch in time but is noted here as: "15C42402B0", for whatever that may be worth.

I know and accept that I have limited electrical know-how of electrical design, but in terms of "isolating" the ground (knowing the car is now negative and "assuming" the radio is positive), the radio along with the antenna, I know how to construct so that the radio and antenna is "floating" or isolated from the chassis. Even if I made a kind of ground (block of metal installed but not coming into contact with any other part of the chassis), could this theorically work, or am I really up the creek without an inverter (assuming the radio is positive)?

The current facts are:

My car was changed from positive to negative but never completed. Everything now is pretty much converted (tach, generator, fuel pump, etc.). The radio was already in the car but never hooked up when I bought it, so I have no idea if it is positive or negative, or even if it is ever going to work.

So, what would be nice at this point is to determine from viewing the pictures below if this radio's polarity setup is easy enough to identify just by looking at it. It is my understanding this radio came later on so maybe my chances of this radio's polar setup being negative is good. If not, then research is needed and I can start searching with the numbers shown.

If the radio happens to be of a positive setup, then what about my idea of grounding above? Any stabs?!

PS - The exposed screwthreads on the back (captioned as "What is this") is designed for support via using a bracket. (Thanks a bunch to Steve, Ray and everyone else here for their constant input).

Paul

 

[Bob_Spidell]

Re: BJ8 Tachometer, "sparking"

You can get a manual/schematic here (price is a bit steep, though):

https://www.samswebsite.com/en/photofact/search/index/samsid/AR_128

 

[pkmh]

Re: BJ8 Tachometer, "sparking"

Bob, I see my model right at the top of the list.

Not too bad price wise. I even found a place in Jersey that works on vintage car radio installations. Maybe when I'm ready, I'll check them out or continue searching on the internet for another and take it from there.

And if it's a negative setup, then I think I can hook it up myself, but I'll cross that bridge when it comes. In fact, all I need to know is its polarity. If I have to pay $22- for that answer, then so be it. But I am in no rush so I'll just be patient for a while.

Thanks again,

Paul

 

[tahoe healey]

Re: BJ8 Tachometer, "sparking"

Is that a faint "+" engraved just above where you have written "what is this"? There seems to be paper lables on the top of the box that may give some clues.
Have you tried Googling British Leyland radio and the numbers you have on the box? You might also talk to Dave Nock at British Car Specialist. They have been in the British car business since the 50's.

 

[pkmh]

Re: BJ8 Tachometer, "sparking"

Tahoe,

No faint "+" that I could find. Wishful thinking though.

The site Bob offered above actually has my model number posted (1BM2131). That's a good start!

The one and only paper label, with writing anyway, is one of those generic labels identifying how that radio conforms to certain guidelines (FCC?). Don't recall exactly but read it more than once over time and never offered specifics to the radio itself. From this, if you think this could offer a meaningful clue, then I will jot down exactly what it says and get back to you.

The other tapings seem to be protective coverings. I peeled back on all of them only to reveil openings, exposing soldering connections. I admit, I was focusing on switches or just about anything that could be adjusted using a screwdriver or some other tool. I reglued all tapings to protect from exposure to the elements. If you have a specific idea what I should be looking for in these openings, then I'll have another look-see.

Let me know what you think.

Thanks,

Paul

 

[57_BN4]

Re: BJ8 Tachometer, "sparking"

Hi Paul,

That screw is likely the AM antenna trimmer which was adjusted for best reception after install. The radio is probably from an MGB or Triumph around 1972 so would be -ve earth.

Take off the lid, there may be a circuit diagram stuck to the underside. You may also see a date code on some of the components. The Motorola transistor on the back has a date code 126 but I don't recognise it. Normally they are like 5812 for 12th week of 1958. The bolt sticking out of the back would have had a metal strap going to the chassis to both ground the case and hold it in.

Andy.

 

[pkmh]

Re: BJ8 Tachometer, "sparking"

Hi Paul,

That screw is likely the AM antenna trimmer which was adjusted for best reception after install. The radio is probably from an MGB or Triumph around 1972 so would be -ve earth.

Take off the lid, there may be a circuit diagram stuck to the underside. You may also see a date code on some of the components. The Motorola transistor on the back has a date code 126 but I don't recognise it. Normally they are like 5812 for 12th week of 1958. The bolt sticking out of the back would have had a metal strap going to the chassis to both ground the case and hold it in.

Andy.

Hi Andy,

I figure when you say "-ve" you mean negative earth? If this radio is from the early 70's, then I am incline to agree it is negative. My Triumph was negative earth and I remember a radio resembling the one in the Healey, but having those 2 AM and 3 FM buttons or similar (been a while).

I will take the lid off soon and check it out. Didn't even think of doing that. Thanks. I'll let you know what's up.

Paul

 

[AH3000MkIII]

Re: BJ8 Tachometer, "sparking"

Here is a radio taken from a BJ8, I have three of these, this one isn't in the best of condition, but you can see the +/- changeover switch that Steve refers to. I can't get to the other two as they are boxed up in the loft, but from memory they both also have this switch.

 

[pkmh]

Re: BJ8 Tachometer, "sparking"

Thanks for that info AH. I do not have that exposed on the exterior casing as you do. But I will take the cover to mine apart soon and see what's going on inside.

I could be wrong, but yours appears a bit older by design, so if I open mine up and find nothing in the way of a switch, then I might assume mine was manufactured only as negative, since it would seem to me as these got newer, they didn't bother making radios to work on positive earth or even the option of switching.

Does one agree with that theory?

Anyway, I will look inside mine and post my results, if any.

Thanks again,

Paul

 

[pkmh]

Re: BJ8 Tachometer, "sparking"

AH and Forum,

Finally took photos of top and bottom interiors of the radio. Still no signs of switches to cross from positive to negative or vs. Noticed filament to bulb is still good, if that's worth anything. Nothing appears to be fried or tampered with, but that's just my guess.

Looks to me this radio was designed for negative setup.

Anybody care to make a further guess?

Thanks,

Paul

 

[Keoke]

Re: BJ8 Tachometer, "sparking"

Well near that small plastic socket is a + and the typical Electrical ground symbol.--Fwiw--Keoke

 

[Keoke]

Re: BJ8 Tachometer, "sparking"

PS: On another thought about grounding or isolating from the chassis, is it possible to create a 'floating ground'

Yes" but it is risky and not recomended. Keoke


that's not part of the chassis? For example, pretend I have a wood or some other non-conductive bracket mounted to the chassis (or bulkhead, if you will), then apply a metallic mass to it and in turn ground the radio that way, maybe it would work?? (I am laughing now because I have no understanding of electrical know-how so I wonder if this idea is ridiculous or possible

 

[57_BN4]

Re: BJ8 Tachometer, "sparking"

Hi Paul,

Your radio is very similar to the Motorola Sapphire fitted to VW's in the early 70s which were negative ground. Here is a pic of a VW radio, if you study the PCB at the top enough you'll see slight differences.

Here is an article about an early 70s BL AM radio which by the circuit diagram has a floating ground and is (I'm pretty sure) positive earth. https://www.spridgetguru.com/TA0037.html

Given that you don't have any firm info on which polarity it is, I'd pay the money to get the schematic as wiring it up incorrectly will cost a lot more than 22 dollars to fix. Post a pic of the wiring diagram if you get one, it should be fairly quick to establish the polarity.

Andy.

 

[pkmh]

Re: BJ8 Tachometer, "sparking"

Yeah Andy,

Looks very close to mine. Even the printed codes found on the circuit board seem to match up.

I'll have to deal with this issue later on.

Thanks for the info though!!

Paul