Colt Excalibur

[jodude1]

I recently came up with an old colt excalibur base (Yard sale) Went through this radio ,new bulbs, cleaned switches ,etc etc. Everything works fine. Radio has been converted for Extra Freqs. Heres my problem ,output is only 2 watts on any frequency . It transmits perfect just low output. I have tried adjusting power output on upper and lower portions of the band but makes no difference .Just a nice clear 2 watts output. I am wondering if it is a final problem . Not even sure what the output transistors are at this point I have no schematic. Has anyone had this experience with this radio and if so what was the problem. If anyone could share what the finals are it would be greatly appreciated . Its great old radio she just needs some TLC in the transmit area.

Thanks
Joe ;D

[Sandbagger]

Dec 6, 2008 10:20:17 GMT -5 jodude1 said:

I recently came up with an old colt excalibur base (Yard sale) Went through this radio ,new bulbs, cleaned switches ,etc etc. Everything works fine. Radio has been converted for Extra Freqs. Heres my problem ,output is only 2 watts on any frequency . It transmits perfect just low output. I have tried adjusting power output on upper and lower portions of the band but makes no difference .Just a nice clear 2 watts output. I am wondering if it is a final problem . Not even sure what the output transistors are at this point I have no schematic. Has anyone had this experience with this radio and if so what was the problem. If anyone could share what the finals are it would be greatly appreciated . Its great old radio she just needs some TLC in the transmit area.

Thanks
Joe ;D

Assuming that your Excalibur is the original domestic 40 channel AM/SSB version and not the AM/FM/SSB Export version, it uses the same Cybernet SSB chassis as the Lafayette Telsat SSB 140. The schematic for which can be found here: www.cbtricks.com/radios/lafayette/telsat_ssb140/graphics/ssb140_sch.pdf.

There is a large ceramic wire wound rheostat that sets the AM carrier power on that radio. That may be all you need to tune. What is the power on SSB? Is it normal or really weak as well?

[jodude1]

Thanks for the info. Its not the export model. The 2 watts I was talking about was on USB and LSB I get the same on a dead carrier on am. Already ajusted the am ceramic coil . I have maxed out all the pots. for power on modulation, alc,for sideband etc. But still transmits 2 watts max. I am baffled. Thinking it might be a final problem but still got good modulation out. Any other ideas?

thanks Joe

[2600]

Have you done the bias-current test for the driver and final yet?

For that matter, see if you have at least 12 Volts DC on the bias-jumper pins on SSB transmit. If not, this would reduce your power even if the final is good.

More than once, we've seen this kind of radio that had the bias current turned up as far as it would go, to get the wattmeter one or two more tick marks up the scale. That boosts the heat load on the RF transistors and can slow-cook a final or driver. Typical clue is a thick layer of black tarnish on the metal tab surfaces.

If the driver won't turn up to at least 30 mA. of idle current, or the final won't turn up to at least 60 mA, it could point to a weak transistor.

Could.

If you haven't peaked the transmit adjustments that are "upstream" from the power stages, try that first. If that's the problem, it's cheaper to fix.

73

[Deleted]

I had the same problem with a Colt 1000 (Back Shadow SSB). I could never the bias close t the SAMS book. However, the trasmit was so out of whack, that when i completely started from scratch, it started DKing normally and swing normally. There were several coils to adjusts.

[Sandbagger]

Dec 7, 2008 0:27:24 GMT -5 jodude1 said:

Thanks for the info. Its not the export model. The 2 watts I was talking about was on USB and LSB I get the same on a dead carrier on am. Already ajusted the am ceramic coil . I have maxed out all the pots. for power on modulation, alc,for sideband etc. But still transmits 2 watts max. I am baffled. Thinking it might be a final problem but still got good modulation out. Any other ideas?

thanks Joe

Well, one of the more common things I've seen is that when people put a ton of extra channels in that radio, the power will drop off fast above 27.700 or so. So in desparation to try to wideband the radio as much as possible, many guys will stagger tune the entire transmit strip to keep the power as balanced as possible throughout the whole 150 or so channels it'll normall do. The problem with that is that while the usable bandwidth will increase, the peak power drops off.

Try checking all of your internal supply voltages and then align the entire radio on channel 19 for maximum power and then see what it'll do. Make sure the bias is set correctly as well. If your PEP SSB power isn't up around 13-15 watts or so (with the ALC maxed out), you may have a weak final or driver.

[dxswe]

Hallo guys I have found a manual to Colt Excalibur
Click on this link and download it.It's a PDF file

www.gianf.net/file/ColtExcaliburSSB2000.pdf

Here is schematic. www.gianf.net/file/PTBM131A4X-sch.pdf

[rifleman]

That one is for the Export Model....

But it is still great to have !!!

Thanks !!!