I picked up a Grant XL that only puts out about way less than a watt on am. The only thing I noticed upon visual inspection it the circled component in the pic is very loose from the chassis. Anyone have any ideas on where to start?
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Grant XL very low AM tx
- Thread starter 338_MtRushmore
- Start date
Not having looked inside a Grant XL before, that part appears to be a voltage regulator or a final, and the insulator has come lose. It is a bad thing for that part to ground to the chassis, which is why that insulator is there, and it uses a plastic screw. The problem doesn't sound like a voltage regulator though, so it is possible that is a final, and the 1 watt you are seeing is coming from the driver, and the final is blown.
What is the part number on that?
What is the part number on that?
Wait, I didn't look. Your driver and final are on the left toward the bottom. It is also possible that is an audio amplifier, but that wouldn't be your problem either. Get the part number off of it, and let us know. We can be sure what it is by that. Whatever it is, try and get the insulator back in place, and tighten it down, as a temporary "fix", and see if that does anything.
I am getting full output on ssb, so I would think the finals are good?
I have a junk grant xl here, and the numbers on this one are D1135
The full part number would be 2sd1135. If replacing the insulator doesn't fix it, I would bet it shorted and fried.
I concur with the Master 
D1135 is the AM Regulator/Amp - the one that usually mounts to the side panel by the rear power cord, power transformer and does the job of mixing carrier power (DC stuff) and AM envelope to generate the DC bias needed for the Driver and Final.
There is also a 220ohm 1 or 2 Watt resistor that goes across the leads of this transistor . Called R193, and goes across the input and output (Emitter and Collector) of this transistor. (follow those wires back to the board and see if they go back to the side panel side where there is a notch at the place this transistor would normally mount at) .Which is TR41 ORIGINAL location and its' driver is a 2SC945 and is TR42 - but this also indicates that the SSB AND AM are separated by the MODE switch and it routes a full 12 volts (or whatever is present at the power cord ) on SSB mode, but goes thru that transistor when it's in AM mode. So if its low, more than likely the 220 ohm resistor is what is working maybe even TR42 - the transistor is not - no audio low power type of symptom.
IF R193 is removed, then perhaps that is why it failed or the loose part itself is not properly dissipating the heat it has to in order to provide the envelope power. So it needs not only a new insulator, mica or ceramic - but to prevent this from happening again, you really should put that 220 ohm resistor in there - it keeps the regulator (TR41) from dissipating too much power to be wasted as heat.
Will post a graphic as time permits in a separate post.
:+> Andy <+:
D1135 is the AM Regulator/Amp - the one that usually mounts to the side panel by the rear power cord, power transformer and does the job of mixing carrier power (DC stuff) and AM envelope to generate the DC bias needed for the Driver and Final.
There is also a 220ohm 1 or 2 Watt resistor that goes across the leads of this transistor . Called R193, and goes across the input and output (Emitter and Collector) of this transistor. (follow those wires back to the board and see if they go back to the side panel side where there is a notch at the place this transistor would normally mount at) .Which is TR41 ORIGINAL location and its' driver is a 2SC945 and is TR42 - but this also indicates that the SSB AND AM are separated by the MODE switch and it routes a full 12 volts (or whatever is present at the power cord ) on SSB mode, but goes thru that transistor when it's in AM mode. So if its low, more than likely the 220 ohm resistor is what is working maybe even TR42 - the transistor is not - no audio low power type of symptom.
IF R193 is removed, then perhaps that is why it failed or the loose part itself is not properly dissipating the heat it has to in order to provide the envelope power. So it needs not only a new insulator, mica or ceramic - but to prevent this from happening again, you really should put that 220 ohm resistor in there - it keeps the regulator (TR41) from dissipating too much power to be wasted as heat.
Will post a graphic as time permits in a separate post.
:+> Andy <+:
LATE BREAKNIG NEWS!
Fresh off the press!
Component side...
Foil Trace side - note the "reverse" ECB - Base is towards rear panel...
When you have something like this - a catastrophic failure - it may have also damaged the MODE switch.
:+> Andy <+:
Fresh off the press!
Component side...
Foil Trace side - note the "reverse" ECB - Base is towards rear panel...
When you have something like this - a catastrophic failure - it may have also damaged the MODE switch.
:+> Andy <+:
I got her opened up tonight, and this one has a 2sd525 in it. Can I try the 2sd1135 from my parts radio, or do I need to order the 525? R193 is there. I also need to replace R131 that was snipped, then soldered and looks pretty rough.
They have similar specs. The 1135 has a maximum collector current of 4A, where the 525 is a max of 5A. I doubt you would reach even 4A. If I had to guess, I would say you should be fine.
It dead keys 4 watts and swings about 11 into the antenna. I'd say that was the problem. The insulator behind it was quite melted and crispy. Hopefully it just came loose and cooked its self. Now I just need to order some grease so it doesn't blow again. Not that I actually use AM, but who wants a broken radio? Thanks for the help guys
Me too, especially since it was an ebay buy. Fortunately I have had pretty good luck with ebay radios, except for that one time, and the time before that...…. Now that I think about it, it's just another form of gambling.
Yeah, ebay is full of liars though. If you see anything that says "Powers on but don't have the equipment to test", or something like that, you can pretty much guarantee it doesn't work, and the seller knows it.
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