-
You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
Newest unident grant LT low AM power.
- Thread starter Low_Boy
- Start date
I believe Q37 is the bias transistor? That tested good but the bias diode for the final was bad. We will see where that takes us.
I am totally confused Final bias diode D503 is a MV1YH. Two diodes. So testing the SMD diode on the little board as two separate diodes is actually good because you .can never get continuity between two diodes hooked together in series. I think at least with all the testing I did with 2 1N4148 diodes.
Next Driver bias diode.D504 what is a MV502?
Next Driver bias diode.D504 what is a MV502?
Driver bias diode is a MV1Y, containing only one diode. That diode directly regulates the current source for the base of the driver transistor.
The final diode was originally MV13Y, with two diode junctions in series inside it. This is necessary because the final transistor's base bias comes from the emitter of a NPN transistor. Calls for twice the voltage of a single diode feeding that base terminal to get the nominal 0.6 Volts out of its emitter terminal, to then feed to the final's base circuit.
73
The final diode was originally MV13Y, with two diode junctions in series inside it. This is necessary because the final transistor's base bias comes from the emitter of a NPN transistor. Calls for twice the voltage of a single diode feeding that base terminal to get the nominal 0.6 Volts out of its emitter terminal, to then feed to the final's base circuit.
73
Two bias diodes are good. Just can not figure why I have good power on SSB and 1 to 2 watt on AM. I have checked almost everything.
Nothing looks touched. I will have to verify with the schematic. Already replaced VR10.
Thanks,
Might want to make sure the carrier crystal frequency is set to 7.800 MHz for AM. If it's been tweaked too far, this can cause trouble.
73
73
The 7.8 MHz is the offset so long as the crystal is adjusted to that frequency properly.
If that crystal has been screwdrivered too far off frequency it can hurt the radio's AM transmit carrier power.
73
If that crystal has been screwdrivered too far off frequency it can hurt the radio's AM transmit carrier power.
73
Thanks Nomad I just wanted to make sure we were on yhe same track. I have SSB doing about 17 or 18. Am is just 1 watt. I will keep everyone interested posted
Nomad I must say it again. You are the man. It was late and I was tired so this still needs to be set correctly. I just keyed the mic. looked at the wat meter and turned the correct can and the AM dead key came up to where it belonged. I am not getting real good forward swing so hoping a good alignment will do. Whoever was in the radio must have put wire ties on the wires after they turned that coil because I could not get to it with out cutting what I thought were factory wire ties..So I will hook up the freq counter tonight and set this correctly.
Thanks
Thanks
