25 LTD Classic

[Sirfredrick]

I have a 25 ltd classic made in 93. It transmits and has good modulation, but can only get it to key up to 1.5 watts. It has new final and I have been reading on some of the things a lot of you have posted to do to maybe fix the issue but has not worked for me. So any other ideas would be greatly appreciated.

 

[sp5it]

What was the power on old final?
How do you measure the power?

 

[Paslong90]

Sometimes we have to increase the preamp (previous stage) to have the proper power at finals

 

[Sirfredrick]

I have a Dosy Test Center, TC-4002-sw. It was the same output as I am getting now which is 1.5 watts. Well I have replaced the TR14 and TR15 transistor. Replaced the TA7301P. What key parts would I have to change in previous stage? It has a 2078 final and a 1957 driver.

 

[Handy Andy]

How good are you at reading schematics?

You just may have to find the cap/resistor - or part - that is in the TX chain causing the low wattage.

So, inspections are in order - any noticeable fresh work on the foil side of the board? Wires that don't seem right - most Cobras have a wiring harness "Loom" where all the wires are tied together and placed to one side of the frame or chassis the board rests in- look for wires soldered with heat shrink or electrical taped in the harness itself - that means repair of a mod done then retied off. These can be places or areas where problems like yours can occur.

Was a modification done to the "Spike" diode - the big one by the Audio Modulator (Transformer) - so that it seems to have some kind of adjustable carrier to make wattage adjustable up or down (like RF gain or Dynamike - does this wattage or carrier adjust instead of what it is supposed to do?)

 

[Sirfredrick]

Sometimes we have to increase the preamp (previous stage) to have the proper power at finals

I am up for any help I can get. Thank you

 

[Sirfredrick]

How good are you at reading schematics?

You just may have to find the cap/resistor - or part - that is in the TX chain causing the low wattage.

So, inspections are in order - any noticeable fresh work on the foil side of the board? Wires that don't seem right - most Cobras have a wiring harness "Loom" where all the wires are tied together and placed to one side of the frame or chassis the board rests in- look for wires soldered with heat shrink or electrical taped in the harness itself - that means repair of a mod done then retied off. These can be places or areas where problems like yours can occur.

Was a modification done to the "Spike" diode - the big one by the Audio Modulator (Transformer) - so that it seems to have some kind of adjustable carrier to make wattage adjustable up or down (like RF gain or Dynamike - does this wattage or carrier adjust instead of what it is supposed to do?)

Thank you I will do i inspection of foil side and check for mods that are not part of the original factory specs.

 

[Handy Andy]

As you look thru the searches for Cobras like the 25 - PC66 and PC-68 are similar styles and can help you in finding a "template" to compare against to help you in rerouting - errors - or other nomenclature that doesn't seem to fit the bill.