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Author Topic: Drake R4C problem  (Read 1031 times)
WB8PFZ
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Posts: 268




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« on: September 02, 2018, 09:38:38 AM »

Seems like everything is breaking lately. My mint perfect R4C has developed a problem. After listening this morning the radio stopped receiving properly. Turn it off for a while and it works. Goes off and this repeats. I am thinking an electrolytic in the power supply. This radio is stock no mods. Any other ideas? Thanks Mike
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KM1H
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Posts: 4722




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« Reply #1 on: September 03, 2018, 11:57:04 AM »

A bit more technical description just may help a bit....
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K4JJL
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Posts: 1071




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« Reply #2 on: September 04, 2018, 05:40:14 AM »

Definitely heat related.  Try some freeze spray, but stay away from the tubes.  Large temp changes can crack the glass.
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WB8PFZ
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Posts: 268




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« Reply #3 on: September 08, 2018, 05:51:55 AM »

When the radio stops working correctly I can peak the noise level on the preselector at 3.5 mhz when the band switch is in the 7 mhz position. But there are no signals just an increase in background noise. Maybe this helps. Maybe a mixer issue? Mike
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WB8PFZ
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Posts: 268




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« Reply #4 on: September 16, 2018, 04:17:35 PM »

After scoping for some signals on the mixer tube it looks like my VFO is dead. Will check some voltages in the VFO circuit. Mike
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W9GB
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Posts: 3340




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« Reply #5 on: September 30, 2018, 07:58:54 AM »

Drake PTO Troubleshooting
by: Mark Gilger, WB0IQK
http://www.wb4hfn.com/DRAKE/DrakeArticles/TechTips/PTO-Repair.htm

Drake PTO : Smooth as Silk
by Neil, K1VY
http://www.wb4hfn.com/DRAKE/DrakeArticles/PTO/Drake_PTO.htm

Drake PTO Service Notes
by Wayne, VE3EFJ
http://www.zerobeat.net/drakelist/drakemod/drmod31.html
===
Drake PTO problems can usually be attributed to
one of the following 4 components:

* Zener diode 1N714
* Silicon diode 1N4148
* Transistor 2N5950, 2N3563
* Solder point on the PTO coil is broken.
« Last Edit: September 30, 2018, 08:03:57 AM by W9GB » Logged
KM1H
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Posts: 4722




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« Reply #6 on: October 02, 2018, 03:19:38 PM »

I doubt if it is heat specific not a problem in that radio.

For starters be sure the crystal oscillator switch is in Normal.

Id suggest reseating the tubes a few times to break loose pin to socket oxidation, maybe use a DROP of Deoxit D-100 applied on a toothpick. Similar to the bandswitch.

It has been several decades since Ive owned C Line and I dont remember if the transistors in the VFO are wired in or plug in.

Carl
Ham since 1955
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WB8PFZ
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Posts: 268




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« Reply #7 on: October 06, 2018, 05:04:31 AM »

Had a little time to play with the receiver. It ran for 10 minutes and stopped working. It seems there is a problem with the LMO or what ever Drake calls it. It seems like it is loose in the chassis. By applying a little pressure it came back to life. Going to remove and see what is going on. Hopefully a bad solder connection or something simple.
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W8JX
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Posts: 13268




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« Reply #8 on: October 06, 2018, 06:59:52 AM »

I would look for a cracked circuit board trace. These can open up with heat. Also try placing a muffin exhaust fan on top of rig. If heat related rig will run longer.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
KM1H
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Posts: 4722




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« Reply #9 on: October 06, 2018, 09:09:05 AM »

That solid state circuit runs very cool but the problems suggested can still occur.
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W8JX
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Posts: 13268




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« Reply #10 on: October 06, 2018, 09:37:08 AM »

That solid state circuit runs very cool but the problems suggested can still occur.

Circuit might run cool on its own but given rig has 10 or 11 tubes in it (depending on version) it is a a coffee cup warmer.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
WB8PFZ
Member

Posts: 268




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« Reply #11 on: October 06, 2018, 11:56:07 AM »

The biggest problem with the Drake receivers is the power supply. They use a 150 volt supply and drop it down to 14 volts. Many have changed the supplies and the radios run much cooler. I am not sure if this is heat related and it looks like it is time to remove the VFO which does not look like a fun project. Oh well............
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W8JX
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Posts: 13268




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« Reply #12 on: October 06, 2018, 12:31:34 PM »

The biggest problem with the Drake receivers is the power supply. They use a 150 volt supply and drop it down to 14 volts. Many have changed the supplies and the radios run much cooler. I am not sure if this is heat related and it looks like it is time to remove the VFO which does not look like a fun project. Oh well............

I have no doubt that heat is a factor here. If is is heat related, even simply removing cover will lower operating temperatures and mitigate problem if it is heat related.
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--------------------------------------
Ham since 1969....  Old School 20wpm REAL Extra Class..
W9GB
Member

Posts: 3340




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« Reply #13 on: October 06, 2018, 02:59:17 PM »

Had a little time to play with the receiver. It ran for 10 minutes and stopped working. It seems there is a problem with the LMO or what ever Drake calls it. It seems like it is loose in the chassis. By applying a little pressure it came back to life. Going to remove and see what is going on. Hopefully a bad solder connection or something simple.
Sounds like a Grounding Issue, that is discussed on the Drake pages.
http://www.wb4hfn.com/DRAKE/DrakePageHome.htm

Drake PTO Grounding
Donnie Garrett, WA9TGT
http://www.wb4hfn.com/DRAKE/DrakeArticles/Drake_PTO_Grounding.html
« Last Edit: October 06, 2018, 03:04:36 PM by W9GB » Logged
WB8PFZ
Member

Posts: 268




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« Reply #14 on: October 14, 2018, 05:00:59 AM »

Last Sunday I removed the LMO from the radio( not that hard). I powered it up with a external supply and monitored the rf output on my scope. It worked for a while and then flat lined ( stopped working). I reflowed a few solder traces and powered it up using the radios power supply. It worked for the rest of the day and I reinstalled it in the radio. It has been working correctly for almost a week. Happy ending. Mike
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