T 368 VFO won't track,help!

[wa1mtz]

anyone know why my vfo won't track? I never opened it up, I had some problems with the gear slipping, got that fixed, put a freq counter on the output, to set the dial. set it at 1500 kc, then when going up, the freq would be off by abt 25 kc. The only place where the mech readout and freq. counter agrees is at 1900 kc. ?? Thanks, mike, wa1mtz@localnet.com

[w1vtp]

I just looked at the schematic for the T 368 VFO and it is of PTO design (the inductor L801) is the tuning element) ... There is a L803 that is probably the calibration inductor but I'd hesitate to tell you how to adjust it.  Assuming you have the manual, just follow the calibration procedure for mechanically setting the dial vs adjusting L803 until the end points agree with the dial.

I'm sure there are some T 368 folks around here that can help.  The manual can be found at:    http://bama.edebris.com/manuals/military/t368/

[wa1mtz]

TNX Al, I downloaded the manual from a site in the UK, looks same size as the bama one. I started thinking it might be a fixed cap, wonder if anyone has experienced this problem? and are the caps located outside the pto or inside?? I never opened the coil up. wonder what's in there?

[WBear2GCR]

Two ways to go.

First line of attack, there are multiple websites and youtoobe vids on fixing the endpoints and calibration (linearity) for
the Collins PTO online. Most are for the receivers that use the PTO. Same thing. Review them. You'll see how it works.

Second line of attack is note the designation on the label. These do come up for sale, even on ebay. You could buy another
one and see how it tracks, and have a backup for parts, etc... The main differences are the freq range and the connectors,
assuming the same basic "can" and shaft for those that are NOT for the T-368. Another one with the same freq range would
be possible to use as a transplant, or modified WRT the connectors.

               _-_-

(Fair Radio might even still have them... dunno)

[wa1mtz]

thanx Bear, I emailed Fair in Feb, didn't have any parts or junkers I was told.
I'll try the searches you suggest. 73, mike 'mtz

[WBear2GCR]

If you don't get direct hits on "Collins PTO" you'll likely find at least one inside an R-390a rebuild/restore page...

[wa1mtz]

I got brave and opened it up ! it is nothing like they use in the Collins ham gear. (not physically) There is one adjustment, a small coil that has abt a 30 kc range. Range is spec'd at 1.5-3, goes from 1360 to 3115, but if I set it at 1500 and then set the mech, at 1500, install, it goes off at odd places,at 10-15 kc off, seems the problem might be in the gears, kinda ruff in spots, not nice & smooth. the main shaft off the knob was hanging down, wobbly, took up the slack by going around the bronze bushing with a small punch in a vise.
That stopped it from wobbling, but there seems to be slippage somewhere else...Think I should look for another unit..might be why this one originally pulled out. Never cud get it to have much output on 14.28,if the vfo is off the multipliers aren't going to align. maybye someone out there has a unit
for swap or sell ??

[w1vtp]

I got brave and opened it up ! it is nothing like they use in the Collins ham gear. (not physically) There is one adjustment, a small coil that has abt a 30 kc range. Range is spec'd at 1.5-3, goes from 1360 to 3115, but if I set it at 1500 and then set the mech, at 1500, install, it goes off at odd places,at 10-15 kc off, seems the problem might be in the gears, kinda ruff in spots, not nice & smooth. the main shaft off the knob was hanging down, wobbly, took up the slack by going around the bronze bushing with a small punch in a vise.
That stopped it from wobbling, but there seems to be slippage somewhere else...Think I should look for another unit..might be why this one originally pulled out. Never cud get it to have much output on 14.28,if the vfo is off the multipliers aren't going to align. maybye someone out there has a unit
for swap or sell ??

[My emphasis in quote]

Take a look at my previous post.  That coil is L803.  It is used to calibrate the PTO.  You need the alignment procedure.  Find it and follow it.  That will fix your problem.  Oh yes.  You may have some mechanical problems also but if you are going to successfully restore this PTO you WILL have to do the calibration and will need the calibration procedure to accomplish it.  Unless, that is, you can find someone who can fix the PTO for you

Al