Long shot. Diagram needed for A&R PLM14 led ppm/vu meter

[Rob Flinn]

As it says in the title. I'm looking for a circuit diagram for an A&R PLM14 ppm/Vu led ladder meter. These were used in Audix conoles, probably amongst other brands. Picture attached

 

[Ike Zimbel]

No drawing, but I will share this: I had an ADR Compex come through the shop a while back, and the fault turned out to be a wire jumper like the one in your pic, behind the switch, next to the blue diode. The solder joint on one end had gone high resistance, and that happened to be the V+ connection to one of the boards.

 

[Rob Flinn]

No drawing, but I will share this: I had an ADR Compex come through the shop a while back, and the fault turned out to be a wire jumper like the one in your pic, behind the switch, next to the blue diode. The solder joint on one end had gone high resistance, and that happened to be the V+ connection to one of the boards.

Thanks for that tip Ike. Unfortunately in this case that is not the problem. I'm not sure if you think this is ADR but I'm pretty sure it doesn't have anything to do with them, it's A&R. I think A&R is what turned into ARCAM the hifi company. On some old adverts I found for this meter when Googling it said the company was in Cambridge U.K which is also where ARCAM (A&R Cambridge) formerly A&R were/are. See this https://worldradiohistory.com/hd2/I...d-IDX/IDX/70s/Studio-Sound-1976-09-IDX-54.pdf

 

[Ike Zimbel]

Ah, you're right, I did think it was ADR. That said, oxidized pieces of 40 year old bus wire are not brand specific .

 

[moamps]

Do you need schematic because you want to make clone of that PPM or for repair? Because as far as I can see, it's a common design.

 

[Rob Flinn]

Do you need schematic because you want to make clone of that PPM or for repair? Because as far as I can see, it's a common design.

Trying to repair. Can you point me to a common diagram ?

 

[moamps]

Could you post hi-res pictures from up and bottom of the PCB?

 

[Rob Flinn]

Could you post hi-res pictures from up and bottom of the PCB?

I will tomorrow when I get back to the workshop. Thanks.

 

[Rob Flinn]

Could you post hi-res pictures from up and bottom of the PCB?

I can say that the leds are driven by individual transistors & that it appears that the current goes through the led's in 2 strings. The first seven green led's are one string & the other seven leds are another. The four comparators are lm339.