Promi 81 desk mic wiring info help.

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original45
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Promi 81 desk mic wiring info help.

Post by original45 » 20 Oct 2018, 19:15

Picked up a PM electronic promi 81 desk mic.
Actually quite a nice little looking mic

Wires in the plug are to four pin plug.
Green no 1 pin
Blue
White
Brown and braid are joined at pin no 4.

Now white and blue are broken off so I need to 're solder them.

Again I'm not technical ,can someone tell me what each colour wire is for as I'd like to wire it to cybernet.
I have no idea what this mic is wired for presently either
Much appreciated.

Thank you
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satelitesid
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Re: Promi 81 desk mic wiring info help.

Post by satelitesid » 22 Oct 2018, 09:40

OK, basic lesson on wiring mics.
You have a number of wires, it doesn't matter what colours they are. All mics are different, and even if you had the proper colours there is no gaurentee that the lead has not been changed or re-wired at some point.
Firstly, remove the plug. Chances are it will not fit, so whip it off. Just cut the wires and unsolder the stray bits.
There is a screened wire inside a braid. That is always audio.
The braid is usually common. In this case it is already tacked to brown, so it looks like brown is common.
Get a meter on resistance, check it works by touching probes together.
Now to find out TX and RX. One lead on to brown, and try blue then white for continuity on rx.
Now do the same with the PTT held down, one test lead on brown, and blue and white in turn.
Cybernet is
Pin 1 is audio
pin 2 is common
pin 3 is RX
pin 4 is TX
As per link

https://www.thunderpole.co.uk/microphon ... ndard.html

original45
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Re: Promi 81 desk mic wiring info help.

Post by original45 » 23 Oct 2018, 17:51

Thank you.

Ok I'm getting at this.
So I can now identify common and I now know how to test the plug on mic lead after following a video.

Few questions.

I hit a problem, firstly when I insert probe into common plug and the other into two other plugs at diff time both have immediate continuity ,and both cease continuity when I key the mic ?.these are green & blue.

The last pin hole is tx as it only has continuity when the mic key is pressed white..

So firstly ,do I need a battery in the desk mic to test it like this or not.

Secondly the mic wire has 6 wires only 5 are used on this 4 pin plug., the common has another wire connected to it , could this be the issue.
How do I proceeded as I can't now distinguish between two wires blue and green. as they do same ,have continuity and it stops when I key mic.

Thank you

Update ,


I believe white is tx as it only has continuity when the mic is pressed or keyed ?.

The brown and the common are soldered together I presume I should leave them together and this wire is the common although when I part them they do not show continuity at all..?.

Just to confuse me more I read this is standard but the cable have 6 wires.the yellow is cut short never connected to the 4 pin plug.
I tested this yellow wire and it has continuity all the time.


Any advice appreciated please so I can get these two desk mics wired up cybernet ,one is the promi 81 ,the other a academy model bsa 6021 cardoid dynamic mic.
Thanks

original45
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Re: Promi 81 desk mic wiring info help.

Post by original45 » 24 Oct 2018, 16:54

Wired it up after eliminating certain wires to test .. I have no rx audio out the radios speaker.. And when I key mic it moves needle across meter and tx light illuminates but I get kind of a dull pop and noise . I having tried it for tx audio out for fear I may damage something in the radio.

original45
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Re: Promi 81 desk mic wiring info help.

Post by original45 » 24 Oct 2018, 18:05

Right I have swapped rx and audio over. Now I have rx audio out of the radio speaker just fine. It still keys up but makes a loud sound from speaker when I key up .
Now it transmits but I have no tx audio sent as I put on another radio to listen too.


I can think what else I can do other than remove the brown coloured wire from the braid common and just connect the common .

Help

Update I separated the common braid from the brown , it won't key up without this.

Tested the plug again with meter I still have two pins no 1 & 3 pin both have immediate continuity when I test each with other probe in common no 2 pin.
Then when I key the mic both loose continuity.

Still have rx audio.and tx but I have no tx audio out and when I key the mic it makes a loud noise through the speaker like a loud scratch or like when the volume controlled are filthy and you get that noise until you use switch cleaner.

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Re: Promi 81 desk mic wiring info help.

Post by original45 » 25 Oct 2018, 15:17

Anyone have a clue what is going on with these two desk mics. Both are wired differently at least the common is in diff place and both have two pins that when are tested have continuity until I key the mic.


What am I missing. This isn't happening on any of the hand mics I have they all are easily identifiable with a multimeter.
But these two base mics are driving me nuts.

Ta

original45
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Re: Promi 81 desk mic wiring info help.

Post by original45 » 26 Oct 2018, 19:14

Tried several wire swaps I have all function except audio on tx.

So I wired up the other base mic the academy.
I have same here ,all working except tx audio.
Radio transmits but no audio.





Any ideas please.

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The Collector
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Re: Promi 81 desk mic wiring info help.

Post by The Collector » 27 Oct 2018, 13:26

Have you got a working battery in? ;) lol

Just wanted to say, I had a Promi about 15 years ago that I bought from off an ebay seller in Weoley Castle in Birmingham, along with some other bits. It seemed good quality and felt quite substantial for its size. I think it was very similar to Motorola and Kenwood-branded ones I'd seen too. The audio seemed reasonable, but I didn't own it for long.

I think it was powder-coated sort of crackle-finish IIRC, so just watch you don't knock the edges as mine had a few bits on the corners that needed touching up with satin paint. The mic' element cover plate can be fragile too scratch-wise.

As far as wiring the thing though, I wouldn't have a clue. I can tart things up, but rarely fix them.

original45
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Re: Promi 81 desk mic wiring info help.

Post by original45 » 27 Oct 2018, 13:42

Yes I like it . has kind of a black coated almost hammerite finish Matt.

I just have this thing for old looking stuff,it hasn't to be the best immaculate or collectable with values.

Yes I put a brand new battery in it to test

I know very little about electronics ,parts and repairs but I can solder a plug and now thanks to tm1 use a multi tester to test some faults .

It has got me very frustrated and I have put both away in a box until my head is clear to further proceed.

I have a feeling its not the mic flex cable to plug wiring thats the issue but somehow a unmatched wire on the PTT switch maybe but as you I'm far from knowledgeable or sure what to look for.

Havnt had a desk mic since my old turner expander 500 back in 80s.

Their not worth a lot and not worth posting off to get wired up.I'm so close I just can't get it .

Only missing the tx mic audio.

Very annoying but I can appreciate its hard to diagnose problem with ought seeing it.

But again neither mic tests as any of my fist mics did ,so either its the PTT wiring not suited or maybe base miCs test diff.

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Re: Promi 81 desk mic wiring info help.

Post by The Collector » 28 Oct 2018, 14:38

I'll have a look in the loft later and see if I jotted down the wiring for it. If however, the wiring was already right for the radio I was using at the time (most likely 99% a Cybernet-based or Fidelity Homebase), then I unfortunately wouldn't have had to mess with it and write down the colours/pins.

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Re: Promi 81 desk mic wiring info help.

Post by The Collector » 28 Oct 2018, 18:28

No good sorry.

I've rarely had base mic's in the past unless to tart up or sell on, but I made a few notes of the ones I've had and had to change around. Unfortunately, most of them were Sadeltas etc as you can see below.

I also had a look at my old lists but they're for CB wiring, not for the mic's themselves:
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original45
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Re: Promi 81 desk mic wiring info help.

Post by original45 » 28 Oct 2018, 19:32

Thank you for looking. Lol you seem to be as bad as me ,I have loads of info on paper for future reference.

I'm convinced it's not plug wiring but the ptt wiring only because they do not test as all my other mics.

For now I have boxed them up .I can't progress with them until I'm sure I know what to do or it will drive me mad and I won't sleep.

It's good to keep such records.

I have been offered big boxes full of radio manuals, schematics so on from a radio repair shop recently closed .
If I could digest them tbey would be of use to me but km not so technically minded.

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Re: Promi 81 desk mic wiring info help.

Post by The Collector » 28 Oct 2018, 22:42

Same here mate. I can solder, so long as someone tells me what wires go where!

Some of those pages are from the early 80's like the 5-tone beep wiring notes, then Astatic and Sadelta wiring in the early to mid-90's with the 007 wiring being the latest about 4 years ago.
I keep them along with my rub-off lettering sheets that I still have from relettering radio front panels, most from the mid-80's.

Good luck with them anyway. It'd be a shame for them to languish in a box, unused and unloved :(

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