I own a Heathkit SB-1000. Have not had it to long, just a few months. Had a few issues and just wanted to share them and what I did to fix them.?

one day on 80M I think I hit a bad something. Bad tune or wrong ant, I¡¯m not sure but had an arc or something. After that, 80 was not tuning up at all. 40M and up worked fine but ones in a while, I could swear I seen and even Hurd an arc. I thought it was the tube, but it was just the reflection off the tube that is visible through the right side cabinet. This started happening more and especially while tuning up. And the breaker kicked off the amp and it went back on.?

I took the cabinet off and had a good view at the area that I suspected was arcing and I noticed the wire from the wound core L9 to the band select was broken. There was a small gap between the wire and the chassis about 1/8 or less and I seen it arc across.?

Also, turn 11 on the 80M/160m tank L8 was tarnished black and the plastic form/turn spacers were melted to the point that the shape collapsed into two pieces, pushing into each other with some of the turns, touching each other. ?

Also, the 2.5mH RF choke fried. It lost value but was not open. This agile junctions with the lead to L9 wound core wire that broke.?

I replaced the RF choke, fixed the wire, pulled the L8 tank out, cleaned with toothpaste, water mix, rinsed with water, then rinsed with 91% alcohol, Fabricated plexiglass, spacers and reformed the tank.?
I also used strips of paper soaked with DeoxIT to clean the relay contacts, a trick I learned from my friend Paul. I tested all of the diodes on the rectifier board, inspected everything, tightened all bolts, including the loose ones that hold the tube socket, they also ground the grids. I did the washer mod on the band select junction that runs to the door knob, capacitor on the plate capacitor to prevent corona. I cut many long leads at many junctions from the original builder. and I cleaned everything.?

now she is working great, here is some of the data I recorded after tune up on several bands.?

160M

68W drive = 600W out

Ig = 150mA

Ip = 380mA

Vp = 2900

Zp = 7632

input = 1,102W

efficiency = 54.45%

?

?

80M?

62W drive = 800W out

Ig = 150mA

Ip = 425mA

Vp = 2900

Zp = 6824

Input = 1,232.5W?

efficiency = 65%

40m

63W drive = 810W out

Ig = 150mA

Ip = 400mA

Vp = 2910

Zp = 7275
input = 1,164W

efficiency = 69.6%

?

20M and 15M Efficiency about 63%

10M?

58W drive = 700W out

Ig = 150mA

Ip = 435mA

Vp = 2900

Zp = 6667

input = 1,261.5W

efficiency = 55.5%

I have ran about 10 hours or so since I repaired the amp and I¡¯m pretty happy. I do not run the limits in the manual, the manual max limits are:

Ig = 200mA

Ip = 550mA

Output power = 1KW

thats nuts and contradicts Eimac data sheet for a 3-500Z

?

Eimac Data sheet max at typical operation at 3KV

Ig = 108mA

Ip = 400mA

output 740W

?

Heathkit manual max limits = 37.5% over Eimac max specs and has you exceeding grid dissipation by 50%. Grid is the most fragile part of the tube.?
Eimac states driving impedance is 115.?
grid dissipation = peak voltage X grid current.?
so at 100W drive, peak grid voltage is 150V

150V X 0.2Ig = 30W grid dissipation. ?30W grid dissipation is 50% over Eimac 20W Grid Dissipation.?

I do runs a little over on SSB, about 150mA of Ig and 400mA of Ip, but on CW I run a max of 100mA of Ig and/or 400mA of Ip, no more.?

well, thanks to my friend Paul for his great mind and others!!!

?

thanks for reading. Hope this helps someone out there.?
KG2RG

Come to think of it... if your ISP won't display A O L dot com, then it may not even allow you to e-mail to A O L dot com.

On 4/12/2025 9:26 AM, Steve wrote:

"That" was supposed to be "at A O L dot com" without the spaces. Your ISP probly doesn't like the A O L part and removed it.

Steve K0XP

On 4/12/2025 8:27 AM, KG2RG via groups.io wrote:

gudguyham@.... Lou.

what is that??? ? Not an email?

--
See my QRZ.com page at

--
See my QRZ.com page at

On Saturday, April 12, 2025, 11:27 AM, KG2RG via groups.io <justinandyazny@...> wrote:

gudguyham@.... Lou.

what is that??? ? Not an email?

On Friday, April 11, 2025, 8:05 PM, KG2RG via groups.io <justinandyazny@...> wrote:

Lou, can you email me. I¡¯m interested in one of those boards for a future fun project. My Email is good on QRZ.
I¡¯ll also try and see if I can private message you here. Not sure how that works but I¡¯ll start clicking on everything hi hi. ?

On Friday, April 11, 2025, 1:01 PM, KG2RG via groups.io <justinandyazny@...> wrote:

Wow, great info from both of you!!?

lou, do you still have any of those power supply boards for sale? Sounds like something handy to have.?

I had read about the power supply being in that air cooled compartment under the RF deck and the first time I had the cover off, I just Took a long stare at the RF deck and wondered how this top cover that all these parts were bolted to would come off. I also wondered why their bottom of the cabinet didn¡¯t have a removable panel.?

I figured the big parts like the tapped tank circuit and band select could and should remain buoyed to that HV compartment lid. I would just need to remove sever connections. Some leads could remain soldered to the RF deck components by simply removing the bolted in terminal to the variable tune cap. The leads that built to the variable load cap would be impossible to get to as the load cap is under the tune cap and so they would need to be on soldered from the components on the RF deck. Tubes parasitics all that would need to be removed. ?The band select has a coupling clamp and may need only one end of the clamp removed. May be a good idea to mar the blame and shaft so they align back to avoid having to re index the band select positions.?
There¡¯s also a little hole with a wire that comes through that panel somewhere in the area between the tube and plate choke. Mrobably should also remove the?

horizontally, mounted, choke, may or may not be necessary, but this was my thinking at the time before reading Lou¡¯s comments.?

my Vp also reads low. On the Vp meter, I think each little line is 60V and so mine is reading roughly 2,175Vp.?
I believe the inaccurate low Vp reading is do to out of tolerance resistors that are likely on the power supply board, 3 at 1meg, and 1 at 150K, all 2W.?
I really enjoy having accurate meters. I have some other amps and I enjoy calculating the plate impedance, input power and efficiency.?

plate impudence = Vp / Ip

input power watts = Vp X Ip

efficiency = output watts / input watts X 100

?

so I never can tell what¡¯s really happening with my commander until I can replace those resistors.?

Have always been interested in how the novice back in the day kept their home brew rigs compliant to 75W input and even the General and up classes back when the legal limit was 1KW DC input to the final amp.?

the Heathkit SB 220 amplifier really amazed me on how they designed this for hams to tune up. This was very clever.

I learned a few interesting facts about the SB-220 and some operational history on how they use to legally tune it up in the old days when the law was 1000W DC input to the final amp. Back in the 60¡¯s when they designed it, the heathkit engineers were clever.?
Because the duty cycle of voice modulation is 50% or less, you could legally operate at 2KW input on SSB. But how do you tune up the amplifier to 2KW without exceeding the 1KW limit??

This is how the engineers made it possible. By using 2 high voltage settings that differ by the square root of 2 (1.4X)

When you tune, the amplifier output network, you are transforming the load impedance to a much higher plate impedance. That transformer and penis remains the same regardless of the plate voltage. Power is related to the square root of the voltage. ?If you increase the voltage by 1.4, you increase the power by 1.4 squared (2X) so you tune in the lower voltage tap to 1KW PEP and then switch to the 1.4x high voltage tap, the SSB position. ?You would only need to possibly increase your exciter drive level to match the same plate impedance but you would not need to adjust the load or plate on the amplifier.

Here is the example of how the engineers intended for everyone to tune up.?

In the CW/Tune position, tune up with your CW key. Stop whenever you want at whatever power out you want and if your using a scope, get your trapezoid linear with the proper amount of loading and dip your plate and all that good stuff. Now that you¡¯re done, make a note of your voltage on the plate and your plate current.?

Vp= Plate Voltage
Ip= Plate Current.?

So if I have the following parameters:
Vp= 2190V
Ip= 450mA

Then I need to know my plate impedance.?
Vp / Ip = plate impudence?

2190/.450=4,867 Ohms.?
Remember this plate impudence because this is about the plate impedance we will need to put the amp at in the SSB high V tap.?

Now switch to SSB high tap and key down fast and take note of the Vp under load.?

Let¡¯s say your Vp=2780V
Vp / plate impedance = the Ip you need to be at in the SSB high tap.?

2780/4867=0.571?
You need to key down in SSB and increase exciter drive lever until your at Ip 571 or close. Say past the 5 and between the 3rd and 4th line is 570mA Ip.?

Ok, your now at:
Vp= 2780
Ip= 570mA

That¡¯s it, your done! You do not need to adjust your load or dip the plate with the tune. You should now be at the same plate impedance in the high tap as you were when you tuned and dip the plate in the low tap.?

Let¡¯s see. Remember our plate impedance in the low tap tune position was 4867 ohms.?

Vp / Ip = plate impedance
High tap values
Vp 2780 / Ip 570mA = 4869 plate impedance. Same impedance you already tuned and dipped your plate in the low tub tuneup.?

Of course you don¡¯t have to do any of that now with our current power allocations but I just love the history of exactly how they designed this amplifier.

some may already know this but I have had many people swear this is incorrect. One friend of mine who

is a brilliant buddy from AM said impossible, makes no sense, not possible. About an hour later he wrote me back and said the numbers and math definitely match up, but I don¡¯t know how this is possible, I¡¯m still trying to figure out and get my head around it, I must be missing something. I have run this test hundreds of times with a scope and every time I have done it, it¡¯s dead on and everything is perfectly loaded and linear with proper load coupling, and the plate dipped and the tube resonant. This is how it was designed and why.?

anyway, I would love to have all metrics super accurate because it¡¯s part of the enjoyment of operating

On Friday, April 11, 2025, 9:53 AM, Bill Cotter, N4LG via groups.io <n4lg@...> wrote:

Hi Louis,

Thanks for the suggestion. I didn't realize
dropping the rear panel was that easy. I hope I
don't have to go through this again, hi!

And, I did get one of your PS boards for the
future, it is a really nice product.

73 Bill N4LG

At 09:25 AM 4/11/2025, Louis Parascondola via groups.io wrote:
>When you want to get to the power supply on
>these amps you don?€?t remove anything on the RF
>deck.? The way to get to the PS is to loosen the
>set screws on the band switch and variable
>caps.? Remove wires from the terminal strip for
>the fan, drop the rear panel, unsolder the coax
>from the balun or at the relay.? Remove wires
>from terminal strip in the back.? Flip amp over
>on side and remove the screws holding the entire
>RF chassis.? Slide the whole RF deck out.? Flip
>it over on the bench and work on it from the
>bottom.? Sounds like a lot but I?€?m comparison
>it?€?s simple.? Since I?€?ve done it quite a few
>times I?€?m down to about 20-30 minutes to yank
>the deck out.? I have a replacement board to
>slap back in fully populated.? Most of the time
>the PC board is scorched and the traces lift off
>the board.? The board is ruined.? Cheap board
>.? Newer boards have masking and traces don?€?t
>lift.? Original carbon resistor change value and
>the HV meter reads low.
>
>
><>Sent
>from the all new AOL app for iOS
>
>On Friday, April 11, 2025, 9:06 AM, Bill Cotter,
>N4LG via groups.io <n4lg@...> wrote:
>
>Justin,
>
>I have a couple of HF-2500 amplifiers I've used for many years and
>experienced the same failure of the meter lamps. The earlier
>HF-2500 (single meter) has two bulbs and the later (two meter) has
>four. I put up with no lamps for sometime and then just gave in to
>fixing the problem when another issue cropped up.
>
>I noticed that the plate voltage indicated on the front panel meter
>of the HF-2500 (dual meter) seemed quite low, and did not match the
>voltage read with a HV probe on the anodes of the PA tubes by over
>500VDC. I decided to fix it, and replace the three meter lamps that
>were not lit. At the time I did not realize what a tall-order
>fixing the HV meter would be.
>
>Lamps first, I replaced the four incandescent lamps with 3800K
>Bright-Warm-White LEDs from a pinball supply company. These are in
>a #47 lamp form factor and are commonly used to replace lamps in
>boatanchor gear with 6.3VAC on the lamp. The current draw was
>something like 25mA each and I wired each meter pair in series. I
>also strapped a .001uf disc across each lamp to keep any RF out of
>the LED.
>
>There is also a published mod to the metering board where you
>replace the 7812 three terminal 12VDC 1A regulator with a 78S12 2A
>regulator. It solves the marginal current supply issue.
>
>The real pain was fixing the HV meter. As you may already know, the
>HV PS board is located under the RF deck. Nearly every part in the
>tank circuit must be removed to access the HV power supply board,
>as well as the front panel and more. It requires all this removal
>of "stuff" to take out a plate under the RF deck components that
>the HV board is mounted on.
>
>When I finally got the HV board out I found that the series
>resistors for the meter had gone way up in value. This probably was
>due to the dissipation in the three marginal wattage resistors, and
>the heat from all the bleeder resistors in the confined space. The
>air flow from the fan has about half of the air going to the
>right-hand tube closest to the fan, and the second half of the air
>passes through the HV compartment before it get to the left tube.
>So the left tube runs at a higher temperature. Go figure.
>
>While I was in the HV compartment I replaced all the filter
>capacitors with 105C types and replaced all the bleeder resistors
>and metering resistors with higher dissipation parts. I left the
>diodes as-is. Once reassembled, it worked great and the HV meter
>read correctly.
>
>After all this work I saw an ad from Palstar who apparently bought
>the Commander line and did a lot of upgrades on the already great
>amplifier. One significant change they made was to install a
>"door-plate" on the bottom of the RF deck to make easy access to
>the PS circuit board. If I ever have to do this again, I will cut a
>door in the bottom, hi!
>
>73 Bill N4LG
>
>
>At 03:24 AM 4/11/2025, KG2RG via groups.io wrote:
> >[]
> >[]
> >[]
> >[]
> >[]
> >[]
> >[]
> >[]
> >[]
> >[]
> >[]
> >
> >Hello,
> >I have a Commander HF 2500. Have not had it to long. When I got
> >it, only 1 of the 4 meter bulbs was working. After about 3 month,
> >the bulb went dark.
> >I believe there is a 12V 1A regulator that
> >supplies the meter bulbs and the relay. I read the pulls are
> >Festoon type and need to be no more the 0.08A each so to not
> >exceed max current and cause the relay to no key. I finally got in
> >there and they are not the fuse looking type bulbs. They are
> >little bulbs with with short leads soldered to the meter board.
> >
> >i finally got in there because I had another Issue with the
> >standby switch. I think the standby switch was intermittent and a
> >relay was not keying sometimes. I started noticing the problem
> >when I would first turn on the amplifier after the short warm-up.,
> >I placed the standby switch into operate and the amp would not
> >key. At first, I thought this issue may have been the regulator or
> >something else, but I started to notice the symptoms would often
> >happen after using the standby switch. I originally planned to
> >bypass the switch and see if the problem went away and then I
> >could replace the standby rocker switch. But when I got in there,
> >I noticed there was another set of poles that were vacant and
> >likely never used so I decided to utilize it those and see how
> >things went. I cleaned all of the contacts and the plugs on the
> >wire wires with deoxIt, And then plugged the wires onto the never
> >used terminals on the other pole. So far it's been great for the
> >past 24 hours. I'll give it some time, but if the problem comes
> >back, then I'll try bypassing it and if the problem still persist
> >during bypass, I'll look to see other possible causes but so far
> >things are good and my fingers are crossed.
> >
> >after messing around with the standby switch, I pulled the
> >metering board out and surprise, it was not the fuse type bulbs.
> >These bulbs had short leads soldered to the meter board.
> >
> >does anyone have a recommended replacement bulb suggestion? They
> >likely need to be 12VDC at 0.08A. I should've used my caliber to
> >measure the size so I'm not sure what size and what type of bulb
> >or where I can source replacements. Any help would Be very
> >appreciated!
> >
> >kG2RG
> >
> >
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