SB610 question

[K5UJ]

Well, I am finally getting around to putting in new caps in the SB610 power supply.  While I have it open I also put on a new power cord.  But then I'm eyeballing around and I see the input and output exciter phono jacks (looking at them on the inside chassis).  I see something that looks weird.  There is a small gap, maybe about one or two mm between the two center pins of the two phono jacks.  One center goes to a resistor that connects to a choke to ground. (A check on the schematic tells me that's fine.)  the other phono jack center is soldered to a copper wire looks like no. 14 solid that's about 3 inches long and goes over to a phenolic standoff that's bolted to one corner of one of the UHF jacks that get RF from an amp before going out to the antenna.  So you have the phono jack from the exciter that on the schematic should be directly connected to the other phono jack gg right out to the amp, but this has that gap and a 3 inch wire going along parallel to the high power UHF jack jumper but isn't directly connected to anything.   But the 610 seems to work FB.  I've been using it and never knew about this.

So, I've been searching to find out if there was some kind of mod that came out but I have found nothing.  Anyone know about this?  Not sure yet if I should undo all that and put it back like it was on the schematic or not since it seemed to be working. 

Rob

[Pete, WA2CWA]

The one jack exciter connection will work if you have a coax-T connector in the exciter coax line to the amplifier. The center T connection goes to the one jack on the SB-610. The other floating jack sounds like the previous owner was using it to sense RF (maybe for a counter, another scope, etc.). You only need the exciter connection if you want to view trapezoid-type patterns.

[K5UJ]

Pete tnx vy much; the 610 is back in the saddle with a T on the input phono jack and seems to work FB.  I can finally get on the air again; been QRT for a few weeks doing things and trying to get around to working on the 610.  don't like to operate without it.  I hope with the new caps the transformer hangs in there.

Rob

[WA1GFZ]

Check the high value resistors around the CRT. My 620 had a number of them drift high.

[WQ9E]

Rob,

Just to clarify, for normal monitoring use you should be connecting through the SO-239 jacks on the back.  You will damage the SB-610 if too much power is applied to the exciter inputs which are intended for around 150 watts peak RF max.  Most of the medium to high power AM rigs have far too much output to be safely used with the exciter jacks.  As Pete said earlier, these jacks are only to be used when connecting an exciter with an external linear amplifier to view trapezoidal patterns.

[K5UJ]

Rob,

Just to clarify, for normal monitoring use you should be connecting through the SO-239 jacks on the back.  You will damage the SB-610 if too much power is applied to the exciter inputs which are intended for around 150 watts peak RF max.  Most of the medium to high power AM rigs have far too much output to be safely used with the exciter jacks.  As Pete said earlier, these jacks are only to be used when connecting an exciter with an external linear amplifier to view trapezoidal patterns.

Check.  Exciter is running through a T with the stem of the T going to a female to male phono into the 610 jack that's connected to the 1 K resistor and choke to ground.  The other end of the T top not connected to the exciter is going through various contraptions until it gets to the pair 3-500 amp.  Amp goes back into the 610 and out via the UHF jacks.   The 610 is spec'd at 1 KW max but I go a few hundred watts over that peak to peak and it seems to be okay.   It has become another one of those "you don't miss it until you have it" kind of accessories.

Frank, tnx for the tip on the resistors.  Unfortunately I didn't see it until I got the 610 all back together and in the feedlines.  I'm a little lazy about pulling it out again  but if you think it is pretty important I will.  I'm runnning it on a buck transformer so the line v. doesn't fry the filaments.  Put in plenty of overkill capacitance in the power supply.  Those two paper wrapped lytics that filter the 600 v. secondary were completely nonfunctioning.    I also replaced the can cap and the three h.v. caps on the CRT supply.

Rob