Viking 500 - HV Time Delay

[kc2we]

Just aquired a Viking 500 and going over the circuit details. Haven't applied any power yet - have to go over the unit and bring it up slowly on the bench with a variac and the power supply only at first. Never worked on a "500" before, but did many T-368's, Viking II's etc.. I see that in the "500" schematic for the supply there appears to be no time-delay for the 866A rectifiers. As I recall, there's a minimum of 60 seconds warm up time for the merc vapor rectifiers back "in the day". The manual makes no mention of waiting 60 sec to hit the HV. So, I am I missing something here or? The Unit I have has 3B28's which do not require the warm up, but just trying to determine how EFJ handled the 866A's without any fireworks. Tnx.

[WQ9E]

They left it up to the user to provide the delay.  Mine came with SS plug-ins instead of 866A tubes and I am no fan of MV rectifiers.  They look pretty but to me they aren't worth the risks and maintenance.

One thing to watch for with your 500 is the T/R switching.  The control relay in the Viking 500 is supposed to provide a slight mechanical delay on release to avoid hot switching but this delay seems to disappear with age.  About a year after I got mine it would sometimes arc across the protective gap from hot switching the output.  I installed a small electrolytic cap and blocking diode across the relay coil to restore the delay and this took care of that issue.

[kc2we]

Tnx Rodger for the tip on the slow release. I saw that same concern in other articles about arc back issues. Any suggestions (if you know) where to get EFJ spray paint cans (maroon & grey)? I also was looking at Chuck Hurley K1TLI at johnsonradioresto.com who does "remanufacturing" of EFJ radios, silk-screen work etc.. I have no reports on his work either way. Just looking to redo the front panel of the RF unit. I'll do the re-capping etc. Tnx Seth KC2WE

[WQ9E]

Chuck does excellent work which is not inexpensive.

Johnson Maroon varies a bit over the years so it depends upon whether you are repainting an entire case or trying to match and repair an existing paint job.  Some of the original units have a considerably darker maroon color than others.  GM has used a very similar paint to Johnson Maroon several times, my 1985 Monte Carlo SS was a perfect match and I realized after I took delivery that my 2008 CTS is a very close match.  The original paint name for the CTS was Dark Cherry but I think GM now calls it something else.

I have not had any problems with the interconnecting cables and those connectors are easily sufficient for the expected voltages.  I believe that most of those issues resulted from a combination of hot switching the antenna due to delay relay issues combined with the owner's manual instruction to increase the gap spacing if nuisance arcing occurs-once this is done then the voltage will arc over at the next closest point.

Also take a look at Jim Garland's ER article about adding inrush limiters to allow fusing closer to the normally expected circuit current.  I made his suggested changes to my 500.  The clipper in mine is intact but turned to minimum so that it does not impact the audio.  I get excellent audio reports and there is no reason to go in and rip stuff out of this classic rig.

[kc2we]

Rodger: Any ideas for the Johnson Viking grey on the "500"? Tnx in advance. Seth KC2WE

[W2NBC]

Seth, Rodger

I am not sure on the grey.. I mixed up a bit of my own once for touch-up.. The maroon is now GM 7191 made by plasti-kote called "Car Color".

regards,
Jeff

[WQ9E]

Rodger: Any ideas for the Johnson Viking grey on the "500"? Tnx in advance. Seth KC2WE

Seth,

I am not aware of any premix grey that is suitable.  The better (generally larger) Sherwin Williams stores used to do a great job with their computer color match system. 

[ke7trp]

Rodger, Can you take a moment to scribble a schematic of the cap/diode on the relay coil mod? Or maybe just explain where the parts go exactly?  Anode/cathode, plus/minus. 

Thank you.

My 500 ate two Dowkey relays due to lack of time delay.  I ended up making a TR switch out of a double pole 20 amp potter relay and that takes the heat and has for a while now.  I would like to have the mod ready so if and when I need service, i can add the slight delay.

My 500 is out of the box new with no mods, It gets great audio reports. Very little needs to be done if you use the EV638 mic.  Its horrible with a D104 due to the low value grid resistor.

As for paint,  I used the "ebay"  spray cans of EF johnson paint on my valiant.  It was close but not exact.  It has to much purple.  I had my Ranger and another valiant resprayed by another fellow ham.  That too, is close but not exact.  To much gloss and metalic. 

I really think the best way to handle this is to take the cabinet down to an auto body supply house and have them Scan and mix the paint for you.   

[WQ9E]

Clark,

Here is the "step by step" for taking care of the lost delay:

You will need a terminal strip (with at least two non-grounded terminals), a 1 KV rated diode, a 10uf @ 250V or greater capacitor, and a small length of hookup wire.

First, disconnect the white wire connected to the coil terminal of delay relay RY-302.  Install a terminal strip and mount the diode on the terminal strip.  Solder the white wire that was removed from RY-302 to the anode end of the diode.  Solder a short wire to the cathode end of the diode that is sufficiently long to reach the now empty coil terminal of RY-302.  Solder the 10 uf capacitor across the coil of RY-302, the capacitor positive lead connects to the coil terminal that is now connected to the cathode end of the added diode.

This provides a slight release delay for RY-302 when PTT is released while the plate transformer relay RY-303  will still release immediately.  10uf provides a very short delay but it was sufficient to take care of the problem with my 500.  A larger value will provide a longer delay but it shouldn't be necessary.  My transmitter started this intermittent flash over on release a few months after I bought it and I installed this modification in September of 2007 and the 500 has continued to work perfectly.

[ke7trp]

Thank you Rodger. That makes sense to me now.  I copied the instructions down and saved them. The next time I have to service the 500,  I will add the delay.  Mine too worked great for a while but about a month later started welding dow keys.  I can see the Potter B relay arc when I release slightly. Its holding up for now..

C

[WQ9E]

Careful because you are also exposing other components to excessive voltage.  The gap in the RF compartment should normally fire when hot switching if adjusted correctly and if not the voltage will find another flash over point-which could get expensive!

The only explanation I have heard about how the relay originally worked was that there was enough residual magnetism to hold it closed momentarily.  Apparently that property goes away with age.

[ke7trp]

Maybe my issue is different.  I have never heard the gap flash.. I just had two Dow keys never let go when I unkeyed so I had no RX.  A good SMACK on the side of the dowkey unstuck them. 

C

[WQ9E]

Well, sometimes old Dow Keys hang up and many times the contacts just build up enough corrosion on the receive side that it takes a jolt to make them work.  But it is odd for you to have two fail on the 500.

Unless you adjusted the gaps (one on the modulation transformer and the other is in the final compartment)  they may well be too wide, setting instructions are on page 28 of the manual. 

When mine started acting up the gap in the RF deck fired.  That transmitter was a favorite perch for my Siamese cat but after the zorching sound she isn't nearly as fond of it   She made a jump that would have embarrassed Michael Jordan.

[ke7trp]

hahaha..    I have a Cat here that has hit the ceiling from loud noises a few times.  I saw her run UP the wall when I turned on the vac cleaner once. 

Never adjusted them and never heard em flash.  Maybe its just bad keys.. They seem to work fine on lower power rigs but this rig did not like em.

C