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As Andy said, the capacitors usually are the issues, or front end overload can kill the diode protection (D101 & D102) in the rx, or very common the first transistor goes 'deaf' (q101 2sc1674). If it is mainly AM/FM weak receive, it is almost always the 2 caps (C41 & C159), which are 2...

By "adjustable drive voltage.." Do you mean changeable by the bias controls? if so, when you say set all to minimum - meaning no gate voltage - then install JP8 and see if any of the gate voltage rises. Basically the gate pins without the transistors installed should not change. If one changes...

Well, I finally got brave enough to try this. I found an Isolation transformer with variable power and a current meter. (Sencore PR570). Unfortunately the Amp meter only reads 2 decimal places. I will probably have to use an external meter to get this right. But, I took a shot, and hit a wall...

Totally sure that is what happened.. but when I opened it the 220K resistor was cut... May have been cut and soldered and the solder gave out.. which is why the amp originally worked then quit on its new owner. I replaced the inductors with proper wire wound 22uH coils. Thanks again for all...

Yeah, a piece of small coax would work better for the RF in wiring...

L304 is used to adjust a stage of the mixer IC. You should be able to scope a sine wave on the inputs or outputs of the halves of each mixer - S042P (one pin will have a mix the other will have a clean sine wave): L303 pin 11 or 13 of ic304 and pin 7 or 8 L304 (output 10 or 12 / 2 or 3) L313...

I do not recall what settings I was using back then, but the Lincoln Service Manual does state to set the CW dead key to 21w and AM dead key to 10w. (it also calls for VR107 which is removed to allow the Front Panel RF Power control) Typically back then, power adjustments were set to slightly...

Thanks, the method is understandable. As the pictures show , there is one Bias pot for the final stage and one for the driver stage. I understand the method of monitoring the radio's input current with the jumper[JP8] pulled, and start with both Bias trimmers at full resistance. VR10's wiper...

I am gonna have to read that through a few times.. The pre-driver and driver are both RT1s. The voltage to these are controlled by the RF Power control through the 2SB827Q power transistor, the 2 output RF1s are at 13.8v. I can only assume someone cranked up VR10 (its maxed right now), which is...

OK.. all the before said.. I ran across one of these, with a blown power trace to the mosfets (rail) It had 2 blown Mosfets of the 4 . from a helpful other post, I have the replacement Mosfets installed, I did all 4 with the closest switching matches. So, now how do you set the Bias current /...

Turns out, one of the two 22uh coils was swapped with a 220k resistor and the other had a hole burned through it. Replacing both and cleaning up the soldering, got it up and running. Screen shots of the video I found help me verify the components. Also comparing to the schematics you all...

The key circuit is a bit different. in this one, it uses a TN2095 for the Key and the same for the Preamp. Both 1n4148 measure good. I will check the transistors next. They appear ok with an OHM meter. And one of the small coils on the left hand relay, has a hole burnt in it.. the other coil on...

Thanks, I will trace it through .

also a great example of the torroid coil glue.

Now you see why I am asking...

I think it is a different generation Palomar..

working on a Palomar 300 mobile amp w four MRF455s, I need the schematic, the keyer board is damaged. RX amp and TX not switching. Roger

Hello, First question, are you measuring the Bias in USB mode? Ok, that may have been a dumb question.. Sorry.. No bias adjustment, as was stated above could be damage caused by a failing component. Have you checked the Bias Diodes? I would lift one side out of the circuit and Ohm them out ...

I still have them. You can email me: Rogerbird1 @ Aim.com