Ticking an old box (Commtron box~)

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un-realistic
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Ticking an old box (Commtron box~)

Post by un-realistic »

Hello all,

Just getting back into CB's after a 30 year gap.

I had an unsuccessful introduction to CBs at 13 years old, my mate had a realistic handheld and I bought (with pocket money) a 2nd hand Commtron CB40F from the yellow paper. Cheque was posted - all that old school stuff.

I never did get the thing going, I bought a power supply, I was given an antenna from my dads truck driver friend, I had no manual, and no clue to be honest, Internet didn't exist and nobody I knew had any knowledge of CB's. I should have subscribed to a magazine in hindsight, but our village shop led me to believe there was no such magazine?

2 or 3 nights a week for about 3 months I'd telephone my mate and get him to switch on his CB on Ch.19 and at 7pm We would try and communicate (he lived less than a mile away) We got nothing .... Nada ! and we so longed for them to work.

Now 3 years on .... I assume my old CB was sold by my mum during her frenzied car boot sale days in the 90's, Nothing was safe! I lost my Amstrad CPC 464 to her car boot sales for the princely sum of £13 , Keyboard, Monitor, 300 Games, Manual ... the lot !

Anyway - Instead of having a mid-life crisis, and out of sheer curiosity I scoured the net one night only to find the HOLY GRAIL (well ...a PDF of the instruction manual for a COMMTRON CB40F) seemingly unattainable in my distant youth. I'm deciding to tick that ol' box! I have just bought myself 2 ... yes .. 2 Commtron CB40F's from 2 separate buyers on eBay (not taking any chances lol) and while I was there I bought up a Commtron VIII 80 CH Am/FM unit.

I bought a good power supply unit and next step is an antenna, SWR Meter, Co-ax and connectors.
I'm after any advice on the above items - Antenna Choice, are all SWR meters the same? what size co-ax ?

The Signal meter backlight bulbs on all 3 Commtron CB's have blown so have ordered 3 bulbs from an Irish supplier.
I have a degree in Mechatronics and am hoping to get these units going although never worked on a CB and just learning the ropes really.
That failing - I may have to send them to a pro for aligning and servicing - Has anyone got any advice or recommendations for this.

Right now though, I could really use an Instruction manual for the Commtron VIII - it seems an odd beast and the tune up / Alignment specs/diagrams would be really handy. I really appreciate help if anyone has a copy of the manual.

Looking forward to the chat.

Mr. Un-Realistic
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Re: Ticking an old box (Commtron box~)

Post by 14CS06 »

Hello

Only this

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Re: Ticking an old box (Commtron box~)

Post by 14CS06 »

Hello

It is the same as Commtron CB 40 F but without FM

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Re: Ticking an old box (Commtron box~)

Post by un-realistic »

Cheers Claude

appreciate that
so is the alignment procedure identical?
I'm having trouble understanding this 80Ch unit 40 AM & 40 FM channels ??

Any pointers on the under powered TX ? (1 to 2W)
Last edited by un-realistic on 11 Feb 2022, 22:36, edited 1 time in total.
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Re: Ticking an old box (Commtron box~)

Post by Auldgeek »

There's not much to these radios, so easy to understand. I do have a copy of the manual for the UK FM version. You can also find it quite easily if you google for it.

https://fdocuments.net/document/commtro ... tml?page=1

It's a slow link and you need to wait for around a minute once you click the download button. Any issues, I have a copy here.
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I've changed radios so many times, I've forgotten what I have :think:
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Re: Ticking an old box (Commtron box~)

Post by un-realistic »

cheers for that - that's a great help

So what have I actually got here - The Commtron VIII 80CH ?
How can it be identical to the 40F?
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Re: Ticking an old box (Commtron box~)

Post by Otter »

The CB40F is UK channels FM only, the Commtron 8 is Mid and Hi bands AM/FM. If you go to channle 16 hi on the commtron 8 and transmit you chould hear a distorted signal on the CB40F on channel 1.
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Re: Ticking an old box (Commtron box~)

Post by 14CS06 »

Hello

Image

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Last edited by 14CS06 on 12 Feb 2022, 20:16, edited 1 time in total.
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Re: Ticking an old box (Commtron box~)

Post by un-realistic »

Thanks Claude,

These are for the CB40F are they?

I've successfully fitted new signal meter backlight bulbs to both the CB40F's today - happy with that

Opened up the VIII and found the unit to be very different inside - Also looking at the rear of the signal meter there appears to be a resistor soldered on to the white bulb wire and the other end seams to have been soldered and now broken off the black signal meter wire solder terminal ??

This has got to be a bodge of some kind hasn't it?

I can't find the other end of the white bulb wire so unsure what been done here - I guess the VII schematics would help.
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Re: Ticking an old box (Commtron box~)

Post by un-realistic »

Marked it up for clarity

Also is the black wire (jumper) supposed to be on the rear of the main PCB (see middle photo)?
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Re: Ticking an old box (Commtron box~)

Post by 14CS06 »

Hello

Schematic for PCB 481902C

Image

Image

Look at R139 and SRF METER are connected to ground

viewtopic.php?f=53&t=57168

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Re: Ticking an old box (Commtron box~)

Post by un-realistic »

Cheers again Claude,

Apologies not quite understanding though,

What are your thoughts?
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Re: Ticking an old box (Commtron box~)

Post by un-realistic »

is the resistor supposed to be there?
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Re: Ticking an old box (Commtron box~)

Post by un-realistic »

is midland 100AM the same as my Commtron VIII?
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Re: Ticking an old box (Commtron box~)

Post by 14CS06 »

Hello

Midland 100M
Midland 150M 120 ch am/fm
PC BOARD 481902C

Image

Image

Image

Image

Image

Image

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