RM203p issue
- Mudslinger
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RM203p issue
A couple of years back I bought a new (or so I thought) RM KL203p from the bay of E.
I didn't actually manage to try it, and it ended up stuck under the bed until today.
It seems to have an issue, when transmitting it is putting put the correct amount of power but when turned to the linear on postion the radio that it is connected to stops receiving a signal. Totally deaf.
I am a bit annoyed that I didn't get to test it when it arrived, but for a couple of reasons it wasn't possible, as I could've just sent it back...
As I am now stuck with it, I may as well see if it can be fixed, what do we think is wrong? Switching relay?
I didn't actually manage to try it, and it ended up stuck under the bed until today.
It seems to have an issue, when transmitting it is putting put the correct amount of power but when turned to the linear on postion the radio that it is connected to stops receiving a signal. Totally deaf.
I am a bit annoyed that I didn't get to test it when it arrived, but for a couple of reasons it wasn't possible, as I could've just sent it back...
As I am now stuck with it, I may as well see if it can be fixed, what do we think is wrong? Switching relay?
Mudslinger - Simon
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- ch25
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Re: RM203p issue
Might be oscillating.
Is red led in front lit when deaf?
Is red led in front lit when deaf?
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- Mudslinger
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Re: RM203p issue
I will need to check for sure as it was my brother testing it, but I think that it was on.
Mudslinger - Simon
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- NightProwler
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Re: RM203p issue
So it transmits ok but when you un-key the receive on the radio is deaf? Sounds like a sticky relay to me.
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Re: RM203p issue
It's the 203P, the 'P' meaning it's got a preamp fitted. These are a good little amp, but are well known for preamp failure causing the fault you describe. Receive preamp failure is usually caused by the antenna being left connected during a thunder storm. I've never seen the innards of one of these, but if it's the same as the bigger ones, then it's a single transistor and I seem to remember, although it's a long while ago, that I used something like a BC107 as a replacement to get them going again. It sounds like you possibly bought one that was returned to the supplier as faulty and when they tested it on a dummy load it would have seemed to work fine, so was sent out for sale again as fully functional - they wouldn't have noticed the preamp receive fault on a dummy load.
Last edited by NM1020 on 18 Dec 2023, 16:47, edited 1 time in total.
- Mudslinger
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Re: RM203p issue
Yes, and if you turn it off and back on it is back to normal until you transmit again.NightProwler wrote: ↑18 Dec 2023, 14:48 So it transmits ok but when you un-key the receive on the radio is deaf? Sounds like a sticky relay to me.
Mudslinger - Simon
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There is no such thing as a Fidelity 1000 which is too good to scrap.
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There is no such thing as a Fidelity 1000 which is too good to scrap.
- Mudslinger
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Re: RM203p issue
It could be, but used on it's own the preamp seems to work ok.NM1020 wrote: ↑18 Dec 2023, 16:46 It's the 203P, the 'P' meaning it's got a preamp fitted. These are a good little amp, but are well known for preamp failure causing the fault you describe. Receive preamp failure is usually caused by the antenna being left connected during a thunder storm. I've never seen the innards of one of these, but if it's the same as the bigger ones, then it's a single transistor and I seem to remember, although it's a long while ago, that I used something like a BC107 as a replacement to get them going again. It sounds like you possibly bought one that was returned to the supplier as faulty and when they tested it on a dummy load it would have seemed to work fine, so was sent out for sale again as fully functional - they wouldn't have noticed the preamp receive fault on a dummy load.
Mudslinger - Simon
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There is no such thing as a Fidelity 1000 which is too good to scrap.
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There is no such thing as a Fidelity 1000 which is too good to scrap.
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Re: RM203p issue
In that case, yes, it does sound like the relay is sticking, or possibly being held in by some voltage leaking from somewhere that's then being released when switched off and then back on again, but just guessing really without having the unit actually in front of me.
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Re: RM203p issue
Transistor voltage is leaking and they are not switching off
Could be bad fets.
Could be bad fets.
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- Mudslinger
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Re: RM203p issue
Thanks for the help guys, hopefully I will get it back this weekend and can get a look at it.
Mudslinger - Simon
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There is no such thing as a Fidelity 1000 which is too good to scrap.
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There is no such thing as a Fidelity 1000 which is too good to scrap.
- Mudslinger
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Re: RM203p issue
I have just had a look at this, taken the covers off and there isn't anything obvious wrong. The Only "FET's" in the circuit according to the schematic are the MOS FETS, which I am pretty sure are ok as the full whack of power comes out no problem.
When the unit is dekeyed there is zero power coming out, but it is preventing any received signal passing through to the radio unless turned off and back on again.
I need to try it with a different radio and patch cord just to eliminate a quirk with the setup being the cause.
At very least it has to be worth a few quid spares or repairs due to the output MOSFETs being ok, especially if someone has an amp with them blown.
When the unit is dekeyed there is zero power coming out, but it is preventing any received signal passing through to the radio unless turned off and back on again.
I need to try it with a different radio and patch cord just to eliminate a quirk with the setup being the cause.
At very least it has to be worth a few quid spares or repairs due to the output MOSFETs being ok, especially if someone has an amp with them blown.
Mudslinger - Simon
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There is no such thing as a Fidelity 1000 which is too good to scrap.
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There is no such thing as a Fidelity 1000 which is too good to scrap.
- NightProwler
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Re: RM203p issue
I still think the relay is sticking. I had the same problem in an RM plug in the wall amp years ago, Changed the RS relay and it worked again. If it's one of those relays that the cover comes off try spraying some contact cleaner in it.
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- Mudslinger
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Re: RM203p issue
The relays appear sealed, I can get a pair of new ones for around £8 so may give that a try.
There is also chance that we may have some at work so will have a look there when I go back in next week.
There is also chance that we may have some at work so will have a look there when I go back in next week.
Mudslinger - Simon
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There is no such thing as a Fidelity 1000 which is too good to scrap.
26TM274
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There is no such thing as a Fidelity 1000 which is too good to scrap.
- NightProwler
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Re: RM203p issue
I remember now there were two relays in mine. Mine was the homebase version. Two new relays and it worked again. Worth a try..
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- Mudslinger
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Re: RM203p issue
Yes it has two.
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Mudslinger - Simon
26TM274
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There is no such thing as a Fidelity 1000 which is too good to scrap.
26TM274
26CT612
There is no such thing as a Fidelity 1000 which is too good to scrap.