rm mod.351/p amplifier missing components

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123hotchef
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rm mod.351/p amplifier missing components

Post by 123hotchef »

Right after purchasing the rm mod.351/p amplifier 2nd hand from ebay it appears to be missing 2 components.

Tr3 and D2

I have not wired the amp up as yet as I am unsure if it will work with these components missing.

Is anyone familiar with these amps

Schematics are here

http://www.cbradio.nl/rm/ServiceManual_ ... NG_ITA.pdf

Its all very interesting where can I learn more?
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Re: rm mod.351/p amplifier missing components

Post by 26TM944 »

D1 and D2 form part of the reserve polarity protection. If D2 is missing most likely someone has wired it up back to front with the + and - and popped the diode. The diodes would if you wired it up back to front provide a near enough short to either shut the PSU down or blow the fuse.

And yes without TR3 it will not amplify properly, this is part of the bias circuit for the finals. You'll need to source those two parts and add them in and check everything else as well.

Was it advertised as parts robbed? or faulty?

Cheers

Steve
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123hotchef
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Re: rm mod.351/p amplifier missing components

Post by 123hotchef »

Hi Steve,

Thanks for the reply.

It was advertised as working that is why I aint happy.
here it is

http://www.ebay.co.uk/itm/R-M-mod-351-P ... true&rt=nc

I have sourced the BD179 transistor and I have some 1N5401 diodes here but it should be a 1N5400 diode I think this diode should be ok shouldnt it?

What other tests do I need to perform on the amp.
I dont know much about this side of electronics and radios to be honest.
But I love to learn.

Lee
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Re: rm mod.351/p amplifier missing components

Post by rocket »

You don't have much luck buying 2nd hand amps on ebay do you Lee? http://www.transmission1.co.uk/forum/vi ... 53&t=40538
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Re: rm mod.351/p amplifier missing components

Post by 26TM944 »

IMHO I would send it back as it has parts missing and unless you are willing to take a gamble on it ... which it might need finals and £70 is a lot to pay for a duffer!

He does say in the advert "I have no reason to doubt why it should not work." - when in fact it would never have worked in its current state.

Regards,

Steve
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123hotchef
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Re: rm mod.351/p amplifier missing components

Post by 123hotchef »

I dont have much luck Steve you are correct.
But it gives me something to tinker with and gain some knowledge.

I have opened a Ebay case for the 351 as it wasnt a cheapie.

But these cases take time!

I have ordered the BD179 but will see what happens with the case first.

Lesson now learnt purchase new!
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Re: rm mod.351/p amplifier missing components

Post by The Collector »

As it was listed as "used" and not for parts/not working/spares etc then you can ask for a refund under ebay's rules. You could try fitting the parts and see if it works but you've then messed with it and he may then refuse to have it back if you tell him that.
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Re: rm mod.351/p amplifier missing components

Post by 123hotchef »

His question was why did you open the case?

my answer was because it was not working.

But he says it lit up ok.

of course the LED will light up!
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Re: rm mod.351/p amplifier missing components

Post by The Collector »

If I'm not 100% sure something's perfectly I sell it for spares/repairs just in case, certainly not "used". Even if I think it is all ok I'll sometimes still do it as a precaution against any mishaps in the post etc.

With regards to the Amp, they ought to make them so that the LED only lights up if ALL the components are working (if it's possible that is).
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Re: rm mod.351/p amplifier missing components

Post by 123hotchef »

you are a honest chap then.
So many are not.
I am sure it would be too difficult to have the LED working if all the components worked.
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Re: rm mod.351/p amplifier missing components

Post by Phoenix »

:wave:
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