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[W3SLK]

I have been watching you document the transformation of this 'basket case' since you started the thread. Obviously its a labor of love because I can't imagine the amount of frustration you have. It seems this amp suffered from 'Russian Doll' syndrome. I know there was a sense of great relief after replacing C8, C9, and C15. The difference is night and day! I'm 'mister all-thumbs'. I used to do the micro/min stuff during my USN tenure. Right now though I'll stick to the tubes. Please forgive me if I continue to sit on the sidelines and continue watching you transform your 'FrankenIcom'.

[VE7RF]

I have been watching you document the transformation of this 'basket case' since you started the thread. Obviously its a labor of love because I can't imagine the amount of frustration you have. It seems this amp suffered from 'Russian Doll' syndrome. I know there was a sense of great relief after replacing C8, C9, and C15. The difference is night and day! I'm 'mister all-thumbs'. I used to do the micro/min stuff during my USN tenure. Right now though I'll stick to the tubes. Please forgive me if I continue to sit on the sidelines and continue watching you transform your 'FrankenIcom'.

Meanwhile, thousands of  SB-220's are  still chugging away.

[W9IQ]

Meanwhile, thousands of  SB-220's are  still chugging away.

Only after similar TLC!

- Glenn W9IQ

[VE7RF]

Meanwhile, thousands of  SB-220's are  still chugging away.

Only after similar TLC!

- Glenn W9IQ

I doubt it.   I own  4 x L4B's..... one since  1977 when I bought it new.  It has a trillion hours on it.  The only issue was the 3PDT  tr relay.   One other issue was   a diode in the FWD  HV  started arcing to open air, like a portion of the side of the diode opened up.   Replaced it..and the tr relay...and all is  well again.  It's the energizer bunny.   I have done a bunch of other mods to  the other 3 though, like  qsk  with vac relays, soft start, replaced the blower with a ebm papst,  grnded the grids, added meter protection, installed 50 ohm glitch +  Buss  HV fuse,and other sundry items.   Tossed the useless oem cut off bias scheme + the useless pair of  50k/50 watt wirewounds.  Added  bias. Power supply runs stone cold.  They all just chug away.

Buddy  4 blocks away has a Tec tec hercules SS amp. Blown finals..and no way to retrofit anything in there.   Ten tec can't  retrofit anything either.   It's literally a door stopper.   BTW, those  BLF  188/189's are now obsolete.

[HAMHOCK75]

Please forgive me if I continue to sit on the sidelines and continue watching you transform your 'FrankenIcom'.

Glad you are enjoying the thread. This has actually been one of my easier restorations. The most challenging was a Yaesu FT101EE which had been owned by CB'ers. They removed parts, put them back in the wrong places, or left them out altogether, replaced ham heterodyne crystals with international CB crystals, ran AM with such high power that the cloth covered wires to the pi-network were turned to charcoal.

With restorations finding authentic or very close to authentic parts can be very time consuming. So far,

1. A 50 cfm, 120 mm x 25 mm fan has arrived from Colorado ( installed )
2. The power connectors ( from HK, still in transit )
3. The anti-vibration mounts ( from France, still in transit ). They are M3 metric expansion or Well nuts.

The remaining item is the 50 degree C, thermal switch that turns on the fan.

Just a few notes in passing.

1. Of all the rigs I have restored in the last six years where prior owner's reported the finals were bad, it was only true about 40% of the time. 60% of the time, the finals were good.
2. I did an analysis of the cost of material to build a 500 watt solid state amplifier. Finals were not the expensive items.
3. I ran across this ad by hobbypc for an amplifier support package. https://www.hobbypcb.com/index.php/products/hf-radio/hardrock-500-power-amplifier-support-package
4. It then occurred to me that you can buy a bad 500-600 watt amplifier for a lot less and if need be, replace the entire amplifier module, just using the rest of the amplifier as the "support package".

I was planning to use this basket case 2KL as such a support package if the finals were bad, but based on my 60/40 experience, the finals proved to be good.

[W9IQ]

I enjoy your blogs of your repair and restoration exploits. Keep up the good work.

- Glenn W9IQ

[KD8MJR]

Nice thread, I was going to buy a used 2KL when I got into the Hobby but the guy wanted to much money for it.  I have repaired several SS Amps but only one tube Amp.  While tubes are simpler I am not comfortable with the high voltage.  I find SS amps to be a lot more pleasurable to work on and I am much more familiar with the circuitry design.

[KM1H]

Only after similar TLC!

As Jim said.

The SB-220 family has to be the most idiot proof high volume produced amp ever. The first indication of a problem was when either the fan and/or motor was too gummed up to turn and the solder melted out of the filament pins or the parasitic suppressor resistors increased to a high value that no longer suppressed.

Carl

[VE7RF]

I have been watching you document the transformation of this 'basket case' since you started the thread. Obviously its a labor of love because I can't imagine the amount of frustration you have. It seems this amp suffered from 'Russian Doll' syndrome. I know there was a sense of great relief after replacing C8, C9, and C15. The difference is night and day! I'm 'mister all-thumbs'. I used to do the micro/min stuff during my USN tenure. Right now though I'll stick to the tubes. Please forgive me if I continue to sit on the sidelines and continue watching you transform your 'FrankenIcom'.

It's either a labour of love....or a love of labour.   Hat's off to the OP  for managing to pull this all off.   

[HAMHOCK75]

Thank you all for the positive feedback.

KD8MJR, it is probably just a coincidence but this 2KL is from Martinsburg. I don't think it was owned by a ham though. 

Last night I calibrated the front panel meter for voltage, current, and Po. Except for the PA1 and PA2 bias adjustments, nearly all the 2KL remaining adjustments are located on the main board in the photo below. It took some time to identify them because some are almost buried under cables. Circled in red are adjustments to calibrate the front panel meter. Circled in blue are adjustments that affect the trigger points for shutting down the amplifier. The shut down circuit also triggers on SWR and input power but those trigger points are not adjustable. The meter adjustments are completely independent from the shut down adjustments which will deserve further explanation. R44 visible at the top center of the board is part of the shut down circuit.



The SPDT relay just under the "R18" sends the input to the amplifier or to another SPDT relay in the LPF assembly to bypass the amplifier. It was the only relay I had to unsolder to clean the contacts because it was too surrounded by parts and cables to pry the top off.

[HAMHOCK75]

I am currently using an HP6274B lab grade power supply to test the 2KL. I found this comment on another web site about the 2KLPS.

By the way, the power supply will deliver close to 25 amps before the protection scheme shuts it down. At 25 amps, the voltage sags to 40, or 1,000 watts input. When the amp is driven correctly, it draws a peak of 22 amps, and the voltage sags to ≈44. Again, that's 1,000 watts input. Like most solid state amps, 50% efficiency is nominal, hence, 500 watts out.

The Icom specification for the 2KLPS is 40 VDC +/-3 volts at 25 A continuous for 10 minutes.

Can anyone with a 2KLPS confirm that the 2KLPS output is closer to 44 VDC at full load? My experience with Icom products and specifications suggests that is not likely but this is Icom from over 40 years ago. 

[VR2AX]

I can't remember exactly now but with a linear psu doesn't it reflect the input AC voltage? Japan nominally 200v (or 100), Hong Kong nominal 220 usually measured around 213, UK nominal 240 (they say 230, mine measured 248 sometimes). Remember, at full amp load, AC voltage will usually drop a bit..

[HAMHOCK75]

One reason I was concerned about the power supply voltage is that it sets limiting level for the input power protection circuit. A simplified schematic is shown below.



The input impedance is set by four non-inductive 100 ohm, 10 watt resistors in parallel forming a 25 ohm 40 watt resistor which feeds the input RF into a two way, 3 dB power divider with an input impedance also equal to 25 ohms. Two clamp diodes, D3 and D4, are 1 A. GU3Z diodes reverse biased by the power supply voltage of 40 VDC. These diodes have no effect until the input power reaches a certain level .

Let’s calculate that power level. Assume that the diodes forward voltage drop will be about 1 volt, then they will turn on when the peak RF reaches about 41 volts. The Vrms for a 41 Vp signal is 41 * .707 = 29 Vrms. Power = ( Vrms **2 )/25 = 33.64 watts at the input to the power splitter. Since the half the power is dropped by the 25 ohm input resistance, then the applied RF power at the amplifier input is 2 * 33.64 watts or about 67.28 watts.

This fits well with Icom’s description on page 11 of the instruction manual where it says protection goes into effect when “3. The driving power from the exciter goes up to more than 70 watts.”

The circuit behavior becomes more complex with the onset of clipping. To show that behavior, a time domain Spice model using an ideal diode model was created with the following results. The source is set to be a 50 ohm source with open circuit voltage of 200 volts peak. This source terminated in 50 ohms would deliver about 100 watts to the load.



The green trace is the RF input voltage at the input to the amplifier. The red trace is the clipped output to the power divider. The blue trace is the dynamic input resistance of the network which uses the vertical scale on the right side.

The M3 sized Wells nuts ( anti-vibration mounts ) arrived from France. They fit perfectly.

[N8YX]

Meanwhile, thousands of  SB-220's are  still chugging away.

None of which offer the flexibility of, say, an IC-2KL/AT-500 pair when run with a corresponding Icom transceiver. Or a K3 and KPA1500.

I've put many miles on tube amps of all permutations (including some homebuilt contraptions) and none offered the ability to rapidly change bands then automatically tune the antenna system for optimum power transfer. Not a big deal if you only operate a couple of frequencies on two bands, using one amp per...but a very big deal if you're all over the HF spectrum with only one station.

My tube amps will keep on amplifying - I don't intend to sell them - but at the same time they aren't the first choice for the majority of my DX hunting endeavors. Much as my 6146-based hybrid transceivers are viewed: Some are great performers but the solid-state gear in use here snags the majority of DX or contest points.

[KM1H]

Meanwhile, thousands of  SB-220's are  still chugging away.

None of which offer the flexibility of, say, an IC-2KL/AT-500 pair when run with a corresponding Icom transceiver. Or a K3 and KPA1500.

I've put many miles on tube amps of all permutations (including some homebuilt contraptions) and none offered the ability to rapidly change bands then automatically tune the antenna system for optimum power transfer. Not a big deal if you only operate a couple of frequencies on two bands, using one amp per...but a very big deal if you're all over the HF spectrum with only one station.

My tube amps will keep on amplifying - I don't intend to sell them - but at the same time they aren't the first choice for the majority of my DX hunting endeavors. Much as my 6146-based hybrid transceivers are viewed: Some are great performers but the solid-state gear in use here snags the majority of DX or contest points.

I dont consider needing the same brand specific radios and matching amp very flexible and none are fault free.

The closest I come with minimal tuning tube gear is the 1959 Central Electronics CE-100V Ive had since 1965 and a near mint National NCL-2000 I picked up a few decades ago. The amp has a tuning chart cheat sheet attached under each control and band switching is almost instantaneous. All my other amps are set up the same going back to my serious contesting and DXing days were seconds counted.
There is no wasted time with cranky antenna tuners either, the amps do that automatically and cover 160-10 plus a separate 6 M 1200W converted NCL-2000 which never needs retuning nor does the TS-830 and transverter driving it.

The best news is that reliability has been far better than what I read on here often about SS amps and some transceivers...Im talking decades and not a few years if that much with some SS.
You want me to list my amps?

Carl