Print

[HAMHOCK75]

I was able to acquire an Icom IC-2KL 500 watt solid state amplifier recently. It was known to be in poor condition and without its companion power supply, the IC-2KLPS. The prior owner said he tried to power it with an different power supply without success. Unfortunately, Icom did not produce service manuals for many rigs of this era, only an operating manual so there are schematics but no part lists.

This is a very old solid state amplifier. It was designed during the CB craze of the 1970’s so US units do not cover above 21 MHz but export units did cover up to 10M. It has been reported that some US models did not have the internal components for 10M but that a $150 retrofit kit was available at one time that added those parts and a new front panel bandswitch to accommodate the 10M manual position. Others have reported that some US models did have all the 10M components internally but 10M’s could only be accessed via an Icom transceiver that sent the proper control signals to the 2KL via the back panel 24 pin, control connector. These units lacked a manual bandswitch position for 10M.

This was the condition at inspection upon arrival.

      1.  All the assemblies that mount to the bottom and rear panel were loose inside. The mounting screws were all missing.

      2.  The 2KL runs off 40 VDC. The +40 VDC input was found shorted.

      3. The ALC potentiometer was damaged possibly in shipping

      4. Vibration mounts for the power amplifier/heatsink assembly are missing

      5.The rear panel DC power connector wires were cut to bypass the connector.

      6. The wires to the cooling fan were cut. The fan has also been replaced with what looks like a blue LED computer fan

      7. Circled in green below is the DC-DC converter assembly under the power amplifier modules. Normally it is located just behind the front panel assembly.



Those two copper tubes above the green box are heat pipes about 1/2″ in diameter and about 9″ long. The 2KL has two amplifiers of 250 watts each composed of a pair of npn, bipolar 2SC2652 transistors. Each amplifier has a machined aluminum plate onto which the power transistors are screwed down. The heat pipes are then sandwiched between those plates. The 2KL does not have the traditional, extruded aluminum heatsink. Those fins forward of the amplifier modules are stamped aluminum plates that are pressed onto the heat pipes.

These questions all relate to mechanical parts.

The installed fan is a ThermalTake TT-1225 shown below. From what I can determine, it is a 40 cfm fan at 19.5 dB. Does anyone know who made the OEM fan and how this compares? As mentioned earlier, there is no service manual with parts list for this amplifier.



Below is a photo of the DC input connector, a anti-vibration mount, and a similar Molex 2×3 connector. The anti-vibration mount fits in a hole about 0.31″ in diameter in the power amplifier/heatsink assembly like a grommet but it has a brass insert that a screw goes into from the bottom of the amplifier. I have not found a replacement for this part. The closest similar parts are anti-vibration mounts for disc drives but they are too small.

The rear panel DC power connector resembles a Molex but the pins are slightly different. It is a six pin connector consisting of two rows of three. I was able to use tweezers to extract the four cut power supply wires from the connector. The remaining black and yellow wires are used to turn on a relay in the 2KLPS power supply.

The Japanese connector pins are narrower than the equivalent Molex 0.062″ pin as shown. I have not found a mating connector for this item although the mating connector for the 24 pin control connector is available on eBay. If anyone knows where the anti-vibration mounts or mate to the DC power connector can be found, it would be appreciated.

[VR2AX]

Check the service manual for the IC-4KL which is available online. The 4KL design was an extension of the 2KL, basically 2 x 2KL plus a combiner. It may at least give some clues.

I acquired a not-too-dissimilar 2KL in 2005, eventually it got going with the 10 mod added, a heck of a lot of work is about as much I can immediately recall!

[W9GB]

The rear panel DC power connector resembles a Molex but the pins are slightly different. It is a six pin connector consisting of two rows of three. I was able to use tweezers to extract the four cut power supply wires from the connector. The remaining black and yellow wires are used to turn on a relay in the 2KLPS power supply.

The Japanese connector pins are narrower than the equivalent Molex 0.062″ pin as shown. I have not found a mating connector for this item although the mating connector for the 24 pin control connector is available on eBay.

Regarding the 24-pin control connector used by Icom from 1976-late 1980s, Molex discontinued the high pin count Nylon shells about 5 years ago, however the 0.062” pins & sockets and lower count (9 or less) nylon shells still in production.
==
I believe the six-pin connector was from JST. 
I no longer have paperwork from that era, so I am unaware if JST still manufactures the Pins/sockets or Shell.

J.S.T. SALES AMERICA INC./J.S.T. CORPORATION
1957 South Lakeside Drive
Waukegan, IL. 60085 U.S.A.
Telephone: +1-847-473-1957
+1-800-947-1110 (toll free)
Fax: +1-847-473-0144

Website: https://www.jst.com/
==

The anti-vibration mount fits in a hole about 0.31″ in diameter in the power amplifier/heatsink assembly like a grommet, BUT it has a brass insert that a screw goes into from the bottom of the amplifier. I have not found a replacement for this part.

Advanced Anti-vibration Mounts
Corporate Headquarters
113 Main Street
Bloomingdale, NJ 07403
https://www.vibrationmounts.com/

Sales Orders by phone: 516.328.3662 
==
Illinois Tool Works (ITW) and Essentra bought local Chicago area manufacturers,
BUT I have not researched (or if those products are now retired).

[N8YX]

That JST connector was used on the JST-100, JST-135 and similar transceivers. I'll occasionally see them pop up on eBay.

Good luck with your project. I have a couple -2KL/AT-500 combos and they play very nicely in full-auto mode with my various Icom transceivers from the period.

[HAMHOCK75]

VR2AX, W9GB, and N8YX. That is all great information. I will be following up on all your leads. There are a number of JST-135's for sale on eBay currently. Some show what that matching connector looks like.

In the meantime, I vacuumed the insides of the 2KL. In the process the short at the +40 VDC input vanished. I can now,

1. apply +40 VDC using an HP6291A lab power supply
2. the bandswitch and band LED's are responding
3. the linear on/off switch and LED are responding
4. the T/R control on the back panel turns on the transmit, amber LED

The 2KL is composed of two, 250 watt output amplifier modules identified as PA1 and PA2. The bias for these amplifiers is to be set at 200 mA. Initially neither one could be set for 200 mA. PA1 had a defective C5 and R9. The defective C5 caused the bias transistor to oscillate at 552 kHz. Once R9 and C5 were replaced, PA1 was easily set for 200 mA. PA2 had a defective R9 as well. PA2 also was easily set to 200 mA once R9 was replaced. R9 and C5 are identified by the red circles below. The parts shown are the replacement parts.



In the photo above, if the two wires in the green circles are lifted, ammeters can be inserted between the wire and the collector. The 500 ohm bias potentiometer can then be used to set the Vbe of both devices while the Ic of each is measured for that Vbe. This test was done to see how well matched the devices are. As can be seen from the plot below, each amplifier does have a matched pair but  the pairs are significantly different between PA1 and PA2. By bottom and top device is meant, the location of the 2SC2652 where the board Icom label and identification can be read correctly, as in the above photo.

It was very gratifying that these 2SC2652's are still good even though the 2KL has been out of production since the late 1980's.

[HAMHOCK75]

In another thread I mentioned measuring the transmission loss of snap on ferrites. This seemed to cause much confusion because many hams do not know that vector analyzers come in two types. One port analyzers and two port types. The one port analyzers are exemplified by the popular Rig Expert or Array Solutions AIM4170 series. One port analyzers are not capable of transmission measurements.

The  most common two port analyzer is the nanoVNA. The following tests will use the nanoVNA to measure transmission. The setup is shown below. This will be measurement of the gain, phase, and input return loss of the 2KL amplifiers PA1 and PA2 indvidually with the nanoVNA driving the input of the 2KL and the output measured at the PA1 and PA2 outputs.



This is the result for PA1. The yellow trace is the input return loss, the blue trace is the gain in dB, and the green trace is the phase of the output. A -10 dB return loss is about 2:1 swr, so the 2KL is well below this.



and PA2.



This is the output of the power combiner where the PA1 and PA2 outputs are summed. Looks like the gain is a bit low at the top of 10M.

[HAMHOCK75]

I discovered that there has been a service bulletin from Icom about the 2KL.



It’s not very clear if they just want C8 and C9 replaced or if they want C8 and C9 replaced and C14 and C15 added in parallel with the new .02 uF C8 and C9 parts. It sounds like C8 and C9 which are SMD parts are being replaced with leaded parts. Taking a hint from VR2AX, I downloaded the IC-4KL service manual to see what was done in the newer amplifier. The IC-4KL manual shows that C8, C9, and C12 are all replaced with .02 uF, 500 V parts, identified in the parts list as DD63 YZ 203Z 500V. These are all .12 uF SMD parts in the 2KL. Since the date on the service bulletin is May, 1989, this must cover nearly all 2KL’s since it is said to have been discontinued around that time.

I was able to find a photo of the PA assemblies in the 4KL where it does appear the SMD parts are replaced with leaded ceramic capacitors. The positions of C8 and C9 are changed. In the 2KL, C8 and C9 are between the output transformer and the power transistors but in the 4KL they are located after the output transformer.

[HAMHOCK75]

From the photo of the 4KL amplifier modules above, it looks like Icom abandoned the use of heat pipes in the 4KL. Instead of the PA modules individually mounted to machined aluminum plates that sandwich the heat pipes between them, the 4KL looks to have the PA modules mounted side by side on a conventional heatsink.

While waiting for the capacitors mentioned in the service bulletin to come in, I decided to the examine the LPF module. The low pass filter assembly can be tested by itself with just a single +12 VDC power supply.



The initial tests were not so good. Most bands showed considerable loss as shown below. The blue triangle at the upper left is the reference position representing zero loss.



It was suspected that the relays that switch the filters needed cleaning. Below is a photo of the low pass filters and the relays. The non-toroidal coils on the far right side are the 10M coils. There will be seven pairs of relays if 10M is installed. There is a 15th relay, RL 15 shown in the green box, for switching between the amplifier and bypass mode. All  the relays are SPST except for RL 15 which is SPDT.



Icom made it very easy to clean the relay contacts. Once the metal cover is removed, the black relays have caps that can be popped off with an X-Acto knife. The contacts can easily be cleaned by dragging a piece of paper soaked in contact cleaner through the SPST contact.



Once cleaned the low pass filter response is as shown below for the 7 MHz filter.



The filters are selected by the connectors J2 and J3 as shown.



This was the result for the 10M low pass filter.

[VR2AX]

Another hint - Scott Malcom / MTS in NW USA used to be a source on this piece of kit.

[HAMHOCK75]

VR2AX, I did contact Scott. here is his reply

Sorry, I don't have the parts you are looking for.
I believe the original fan is about 50CFM, of course very old school.
Sounds like the 2KL has the LPF mod in it.  Switches and front panel have been gone for almost 30 years now.
The molex connectors I have seen for sale on Ebay.
Scott Malcom
MTS

I did learn the computer fan is a lessor replacement and will be looking for a fan capable of 50 cfm like the OEM fan.

Meanwhile, I took the front panel apart to see if the band switch had a moveable detente position that might allow an extra position to accommodate 10M. The front panel band switch for the 2KL is missing the position to accommodate a manual selection of the 10M band even though the front panel board has the hole drilled for it as shown circled in red in the photos below.

[N8YX]

One of my IC-2KLs is the U.S. domestic model (no 10M bandswitch spot) while the other is an export (and can be manually placed on 10M). The domestic unit had the 10M mod added at some point and both amplifiers can be remote-controlled to select that segment by a corresponding Icom transceiver.

Something to consider if you have an IC-720, 745, 751 or other rig with a pre CI-V control bus available and can add the required input/output/LPF components.

[VR2AX]

Memory fades but I do recall that a '10m mod kit' was available in and before 2005. This may have included a new band switch which had to be wired in, I am pretty sure the end product was that the 2KL worked on 10 without having to be switched from the Icom radio. The only quirk was there was no 10m position marked on the front panel. I had (still have) a 751A ('F' model) but I never had to worry about the switching logic.

[HAMHOCK75]

I was interested in trying to interface the 2KL with a current Icom transceiver like the IC-7100. It looks like it can be done but takes some effort on transceiver side.



The 7100 has a 13 pin DIN connector with female outputs. It looks like the band control lines needed for the 2KL are the +8 VDC from pin 1, and the band voltage output from pin 5 but from the factory pin 5 is not connected to anything. The instructions for what to do are on page 19-11 of the full manual which is nearly 400 pages in size.



The drawing from the manual is not all that clear, so here is a photo of the pads that need to be solder bridged to bring out the band control voltage line.



I have done the bridge, now to make a cable to get over to the 2KL. The 2KL rear panel connector has a mating part, Molex p/n 03-06-2242. About $25 on eBay. Searching on the Molex p/n shows that the price was about $0.83 from Allied in unit quantities before they were discontinued.

The 2KL did not come with the matching 2KLPS power supply. I am probably going to try a switching supply. I did notice that the 2KLPS has a two stage turn on using a pair of relays. The manual only mentions that this is done to prevent too high an inrush current on the input side and not to any sequencing need on the output side. Looks like a relay will need to added to the power supply anyway since the front panel on/off switch of the 2KL was only intended to turn on relays not to have 120/240 VAC applied to it directly.

[HAMHOCK75]

I made the cable to create the SEND, +8 VDC, and Band voltage signals to the 2KL from  the 13 pin Din ACC connector on the back of the 7100. It worked, the Icom 7100 can control the 2KL through all the bands from 160-10M.

During further testing, the computer fan which tested good never turned on.The 50 degree C thermostatic switch that turns on the fan was tested. A thermocouple was pressed against the aluminum block next to the sensor with thermal grease while the temperature of the block was increased with a heat gun. The sensor did not close until the temperature reached 70 degrees C. It turned off at 39 degrees C. That might explain why the wires to the computer fan were cut if a prior owner thought it was the fan that failed. Now looking for a replacement thermostatic switch. A 50 cfm fan is on order to replace the 40 cfm computer fan. It may arrive tomorrow.



I may have found the oscillation problem mentioned in the Icom service bulletin. At a drive level between 22-25 watts from the 7100 on 160M, the 2KL may be starting to oscillate with the appearance of ripples and spikes. Shown below is the collector signal of the two 2SC2652's in PA1. This did not happen on any other band.



The amplifier was immediately shut down since the measured peak voltages exceeded the Vcbo and Vces of the 2SC2652 which is 85 VDC. It is easy to measure the collector voltages since the output resistance of the devices is about 5 ohms with 300 pF in shunt. The scope probes used are x100 probes with about 5 pF input capacitance.

The .02 uF capacitors have come in so I will be changing the .12 uF SMD capacitors on PA1 and PA2 shortly and retesting per the service bulletin.

This video was found regarding repair fo the 2KL. At about 6:40 into the video, he shows PA1. The PA1 in his 2KL has the redesigned PA1 board where the capacitors C8 and C9 moved after the output transformer same as shown in the 4KL manual.

https://www.youtube.com/watch?v=6d8VBdZvkOo

[HAMHOCK75]

I waited until the new fan came in before changing the capacitors on the PA1, 2 amplifier boards. The new fan is installed but due to the bad 50 C. thermal switch, the switch is bypassed so the fan turns on whenever the 2KL is in SEND mode.

This the result after the original .12 uF ceramic capacitors were changed to the 0.02 uF ceramic disk capacitors at about 25 watts drive measured under the same conditions as in my last post above.



Below is a photo of where the .12 uF capacitors were removed. Instead of changing just two capacitors as called for in the service bulletin, I changed  three as in the new version of the board shown in the 4KL manual which means C8, C9, and C12.



The .02 uF capacitors were added but due to their larger size, one had to be laid down so a wire could go over it and two were connected directly to the collectors of the 2SC2652’s instead of the old pads. I suspect that might have been the reason Icom updated the board.