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Topic Created Posts Views Last Activity
Heathkit SB-200 Restoration & Problem Sep 16th 2014, 15:33 3 2,193 on 17/9/14
28-V, High Current Power Supply - Adjustable? Apr 20th 2014, 13:35 2 1,622 on 21/4/14
G5RV Configuration Question Dec 20th 2013, 23:22 3 1,478 on 21/12/13

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Heathkit SB-200 Restoration & Problem Steffen on 17/9/14
Thank you Martin. It turns out that the ANT RELAY was NOT switching correctly - just as you expertly suggested. The reason was the way I wired the DIN connector from the exciter. The Kenwood TS-530S manual illustrated the pin numbering from the solder side. Therefore, I had mirrored the connections. I found this out when I decided to manually short the ANT RELAY leads. That keyed the amp. After rewiring the DIN connector, I tried the full feature set of the amp and all worked really well. I restored this electrically and refinished the cabinet as well. It looks like it just came off the shelf and performs that way too. Thank you for your help. 73, Steffen (KA2KNX)
Heathkit SB-200 Restoration & Problem Steffen on 16/9/14
I just restored a Heathkit SB-200 linear amplifier. I installed the Harbach power supply and soft-start circuit. (The soft-key circuit was already in the unit when I acquired it last month.) I installed the Harbach power supply that is made for 240V operation. (The only difference are the 20K power resistors as opposed to 10K.) However, I am currently running the unit with the transformer primary configured for 120V operation because I wanted to initially perform some tests with it connected to my isolation transformer and variac.

The preliminary tests were good. The next step was to connect it to my Kenwood TS-530S transceiver in CW mode. (I am no longer using the variac. I plug it into a 120V wall outlet.) . I made a cable going from the DIN connection on the back of my TS-530S to the SB-200 ALC and Ant Relay RCA jacks. I wired them according to the diagram in the Kenwood manual. Pin 6 of the DIN goes to the ALC center connector on the SB-200. Similarly, pin 4 of the DIN goes to the SB-200 Ant Relay center connector. Finally, pin 2 of the DIN is the shield that goes to the outer ground connector on both RCA jacks.

I connected the SB-200 RF Output to a dummy load and the SB-200 RF Input to the output of my TS-530S. I was able to tune up the TS-530S straight through the SB-200 for full exciter power.

I turned on the SB-200 and observed 2400V HV at 90ma. idle current. Then, the big moment came. I keyed the TS-530S, heard its relay and the relay of the SB-200 click, but the SB-200 meter and the dummy load meter both only measured 100W! That's only the exciter's power output. I looked at the plate current and it indeed increases from 90ma. to approximately 300ma. during excitation. Nonetheless, the power output still measures 100W on the SB-200 meter and the dummy load's power meter.

One other peculiarity is that the SB-200 relay will only remain actuated if I use the VOX on the TS-530S. If I manually throw the SEND switch on the TS-530S, the SB-200 relay will not remain actuated during my CW characters. I can certainly live with this behavior if it's expected, but mention it as a possible hint to my problem.

The cable that I made from the DIN to the RCA jacks has continuity and no shorts. The only possible error could be the pin connections. I went by the TS-530S manual and assumed that the DIN plug shown with pin numbers was the external side of the plug. Moreover, since I hear the relay being thrown, I assume that the Ant Relay connection is correct.

This is the first linear that I have ever owned and a piece of history, in my opinion. Any help in getting it back online would be greatly appreciated. (You can see my station on QRZ. I am KA2KNX.)

Thank you.

28-V, High Current Power Supply - Adjustable? Steffen on 20/4/14
I am referring to the project on page 17.36 of the 2014 ARRL Handbook. It is just what I need but for one feature. I need the output voltage to be variable between approximately 5.0V and 24.0V. My question is: Is it possible to make the supply adjustable over that range by changing the values of R8, R9 and R10? I want to build a supply that can output between 5.0V-24.0V at 10A.

I am seeing that it is not easy to find the transformer listed in the project description. Therefore, I would like to substitute it with a Hammond 28V 6.25A (CT @ 14V at 12.5A) . I realize that the supply current rating will drop from 15A to 6A, but that is fine for my needs. Yes, I would like to have a supply that covers the voltage and current requirements of the newer linear amps as well, but it does not seem possible due to the availability of the Avatar transformer.

Thank you,

Steffen (KA2KNX)
G5RV Configuration Question Steffen on 21/12/13
Thank you for a very complete answer. I will work on this and report back. Once again - just what I needed to know!
G5RV Configuration Question Steffen on 20/12/13
I live in an apartment building and want to put a G5RV on the roof. I have to keep the entire structure out of view from the street, and also avoid running coax on the roof surface. These restrictions necessitate my taking a bit of liberty in the placement of the G5RV.

The roof is about 60ft above ground. I do not intend to invert the G5RV, but rather support both ends by stringing them up to two convenient tie points on the roof. My main question concerns the 31ft 450 ohm ladder line matching section. I read that the ladder line should come away from the flat-top at a right angle for at least 15ft. Can I run the ladder line down the side of the apartment building brick wall and near a fire escape, or will the brick wall negatively effect the intended properties of the line? Furthermore, can the antenna be about only 5ft off the surface of the roof and still give good performance?

Thank you - KA2KNX

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