Gates transmitter

[MikeKE0ZUinkcmo]

I brought a Gates 500GY home this weekend and plan to have it up and running on both 160 and 80, this time next year.   I would greatly appreciate anyone out there running one of these, who might be willing to share a little modification advise.

I think this thing needs a couple handles on it so its easier to lift.  

[KD0HUX]

  Nice rig keep us posted

[DMOD]

Cool and brings back memories!

This was one of the first BC transmitters I ever worked on.

Phil - AC0OB

[W9ZSL]

I have a schematic for the BC 250GY which is probably similar to the 500.  810 tubes driven by an 813 in the RF with an 807 oscillator and 810's driven by 6L6's audio?  If you don't have a schematic I can help you out.  We had an earlier 1947 vintage Gates 250 watter as a standby at the station where I worked .  The audio was fantastic!

[MikeKE0ZUinkcmo]

Thanks for all the replies gentlemen.   After getting a bath and some cosmetic touch-up, this will require some investigation to find out "what is" and document same, then return it to essentially "stock" with the exception of PTT accommodations.   I have a manual off the internet, and a copy the original installation manual with schematics.   The schamitic is in the link of my first post.

AFN
Mike     

[DMOD]

In broadcast service, the only components I recall failing were the capacitors in the audio driver and modulator.

Caps. C4, 5, 6, 8, 9, 42, and 44 would fail when the cabinet temp became too hot.

Otherwise, it was a solid performer for the local Mom'nPop stations.

Phil - AC0OB

[flintstone mop]

The 500 is 810's for modulator and an 833 RF final, 807 oscillator? ,813 RF driver and I do not know the audio driver tubes.
Very basic and nice simple electronics that probably sounds GREAT!!
Fred

[W7TFO]

Hi Mike,

Gates used the same output network for over half a century.  A simple "T" net for harmonic suppression, as opposed to the usual ham PI net.

You can simply cut & try a bit at low RF levels so as not to have HV and burned fingers, a grid dip meter is a real help here.

The "T" cap may be shifted for better efficiency, a variable subbed in here will make things easier.

The good thing is all of them are larger than you need for 160/75, so conversion is mostly engineering work and not spending $ .

The coils can be multitapped for band change, as well as the driver LC net.  40 is doable, but the long leads make it really tough to stabilize.

If you muster up around 5W to bat the 813, a VFO input is easy as it eliminates one stage (the 807).  If less drive is planned, the 807 is easily pressed into service as a gain/buffer.

Get yourself a real broadcast limiter with a hard balanced 600-Ohm output, not some consumer thing for PA use.  Don't over EQ, your transmitter is HI-FI, so try and run it as open and natural as possible with a good mic like an RE-20 or even an SM-7.

Look to get some 95-98% negative peaks, with limiter polarity favoring the positive without too much asymmetry as it will just make things uncomfortable.

Have fun, put it on wheels, and you will enjoy it forever.

73DG

[MikeKE0ZUinkcmo]

Phil, 

Thank you for the information regarding the usual suspects.

Dennis,

Thank you for the advise.   This unit has had the oscillator modified to be an AB2 amplifier, so It should be pretty easy to drive it with just about any source.  I'll be using the old Measurements' 59 dip meter a few times I suspect.   There are a couple of side notes about inductor taps being marked, and I looked but if they are there, they're not obvious.  No plans for putting it on 40, but who knows what the future holds.   The audio response as is, is fine, don't see any reason to do any equalizing.

I won't start on it for a couple months, but I'll post as work progresses.

Thanks again to all.

AFN

Mike

[W4RFM]

Please let us know how it goes, your lessons learned will be appreciated by all.
I have a box of 807 pulls if you want some, message me. Just pay postage.
Bob