Keying Expert 1.5K-FA amp

Ed K5YZW · June 2020

After working flawlessly for over a year, my Flex 6700 stopped keying the Expert amp which is through TX1. My TX profile has not changed and has RCA all the TX1 boxes checked. The cable was made by Dan Tassell. Any ideas would be much appreciated.

Steven WA8Y · June 2020

Is the cable still engaged in TX1 RCA socket? Do you have contact closer at TX1?

Ed K5YZW · June 2020

Thanks Steven. Yes the cable is in TX1 RCA socket. In fact, I changed the TX profile to TX2 and TX3 and moved the cable to those RCA jacks and it still doesn't work.

Patrick · June 2020

Call or E-mail Dan, and try power cycling the amp to reset it’s internal devices....if you have not already done so...

Ed K5YZW · June 2020

Thanks Pat. I talked to Dan and he didn’t have any suggestions other than something wrong with the TX Profile. I did cycle power on Expert but no change. When this first happened early this week, rebooting everything fixed it but not now.

Brian Morgan VK7RR · June 2020

Ed, using a meter, check to see if your TX1 socket is being grounded when you hit the PTT. That will help you to identify whether it is a Flex problem or a linear problem. The fact that none of your Tx outputs engaged it, suggests an issue with the linear. If the Flex grounds on transmit then you have an issue with the PTT line in your linear

Larry _ NY8T · June 2020

Check for continunity with an ohm meter on the cable end during radio TX
Manually key the amp by some how shorting the rca jack.
That will narrow down the problem.

David - KO1C · June 2020

I've had TX profiles go "bad" and once I replaced them, all was well again. Good luck!

DV · June 2020

If you are using ver 2.1# or 3.1#, under the main "Settings" menu on SmartSDR, click "TX Band Settings". Look for the band you have selected and then in the right-hand columns make sure the RCA TX output (i.e. RCA TX1, RCA TX2 and RCA TX3) is checked for the outlet you are using to key the amplifier.

Mark_WS7M · June 2020

I suggest you rule out the obvious first:

Test 1 - If the SPE amp is on and you close the connection at the RCA TX port with it selected as the active input, does the SPE amp switch to transmit mode. If not then try the second input. If neither work then you have an issue with the amp. If both work move to Test 2.

Test 2 - Put a volt meter in continuity mode across TX1 RCA on the flex radio. In SmartSDR set tune power to 1 watt. Hit Tune button. Does the RCA jack on the meter show continuity? If so and test 1 was also a success then you need to check your RCA cable. It may be bad. If your RCA does not show continuity during TX then go to test 3.

Test 3 - if using versions 2.1# or 3.1# as suggested by Doug, open Settings, TX band settings and make sure the correct RCA ports are checked on for the bands you intend to operate AND for the test band you are on right now during these tests.

Note! Older versions of SmartSDR have the enable of the TX RCA ports in different spots. The goal of this test is to see if the Flex radio is closing the RCA port when it goes to transmit. You will need to look around for settings and play with them.

Test 4 - If test 1 is a success but tests 2 and 3 are falling then I suggest a radio factory reset. After the reset create a brand new profile. Go back to the various settings screens and enable the TX RCA port. Retry test 2.

Through these tests you will find one of the following:

1) SPE amp does not key when RCA TX input is shorted. SPE amp problem. Arrange for service

2) Flex radio is not closing contact on TX RCA. Arrange for service

3) RCA cable was bad, replace and retest

4) Settings were not correct in radio setup. Correct these.

5) Lastly you could have problems with both SPE and Flex. Hopefully not.

Ed K5YZW · June 2020

Thank you all for the help. I tried all suggested tests. Everything passes--the wiring is good and the Flex is sending the TX1 signal which apparently is being received by the Expert amp. For some reason the Expert is not responding. I have emailed Bob with Expert Amplifiers and will see what he thinks the problem might be. The FlexRadio Community is great!

Mark_WS7M · June 2020

Ed, Bob just repaired my poor lightning struck 2K FA in record time so he will take good care of you.

But I am curious. You say you tried all the tests and I believe you. Did you try shorting the RCA input to the SPE amp? Does it go into transmit or not?

Ed K5YZW · June 2020

Bob, Dan Tassell who makes cables for Bob told me that the Expert uses a transistor and not a relay so shorting the RCA input would not work. Is there another way to test it?

Clay N9IO · June 2020

Ed just disconnect the cable from the amp and short the RCA connector tip to shield (ground) if the SPE is working you will see the red transmit light go ON on the front of the 2K.

Doesn't matter if it's a transistor switch or relay or shorting taking it to ground, the result is the same. Just a little basic trouble shooting to determine if the PTT input to the amp is working, if it is then we go backward to the cable.

I am confused also you stated
"Everything passes--the wiring is good and the Flex is sending the TX1 signal which apparently is being received by the Expert amp. For some reason the Expert is not responding."

Ed if the PTT is being switched to ground (receiving the signal) the amp red TX light will go on. Is that happening? Also, what is it that is not responding?
This information will go a long way.

Ed K5YZW · June 2020

I shorted the RCA input RY1 and the red transmit light came on. So it appears that the Flex is not doing its job. What should I try?

Craig_KØCF · June 2020

OK, now try plugging the RCA cable back into the amp and unplug it from the Flex. Using a screwdriver, short between the center pin and sleeve of the RCA plug at this end of the cable. Does it key the amp? If not, the cable is bad.

Mark_WS7M · June 2020

Yes Ed, this is a process of checking each piece. If I'm not mistaken:

1) You have confirmed that if you put your Flex in tranmit that you see continuity across the Flex RCA TX1 output right? The best way to test this is to sacrifice a known good stereo RCA cable. I have about 10,000 of these laying around from various VCRS, TVs etc over the years. Anyway you but the cable like 3 inches from the RCA plug. You will find a shield and a center conductor. Plug the RCA plug into the Flex RCA port. Put your volt meter leads on the shield and center conductor you just cut. Now put the flex in tranmit. 1 W on tune should do it. Does the meter show continuity? Does it beep? If so the Flex is closing the connection.

2) You claim you just did this. But if you take the same sacrificed RCA cable and plug it into the RCA input on the SPE amp and short the center and shield together the SPE should go into transmit mode. Red LED and display should change.

If 1 and 2 are good and you see continuity and SPE goes into transmit then your RCA cable going between them has to be bad.

Clay N9IO · June 2020

Ed,
Be sure to go into TX Band Settings and confirm you have TX1 TX2 and TX3 checked on for each of the bands al well.

Ed K5YZW · June 2020

Thank you all for the help. I did verify that the SPE was being keyed but there was no power output. I got on the phone with Bob Hardie, the U.S. rep dealer for SPE Expert amps, and he took me through some checks and determined that it looks like a MOSFET failure. So I am boxing it up to send to him. Thanks again. I will post the outcome. 73, Ed K5YZW

Clay N9IO · June 2020

Sorry to hear Ed wish it were a simple fix for you.
Good luck.

Clay N9IO

Ed K5YZW · June 2020

Clay I doubled checked the TX1,2 and 3 boxes are checked in the TXBand Settings. I also tested the TC1, 2 and 3 sockets when transmitting and they registered on the ohm meter.

EA4GLI · June 2020

This happened to me on the 1.5k.
The explanation from SPE Italy was that the relay for band change got "stuck" and when I TX on a different band it blew my finals [sic]. I had to send it to Italy and it got repaired under warranty, but I had to pay shipping both ways and wait for 3 months!!
Hopefuly you get a better turn around with the USA SPE Service.

Ed K5YZW · June 2020

At least SPE made good on the warranty. Mine is still under warranty so we will see. Bob Hardie said he could turn it around fairly quickly as there are 4 ahead of me.

Mark_WS7M · June 2020

Good to hear you figured something out.

Bob just repaired my lightning struck SPE 2K FA very quickly.

Ed K5YZW · June 2020

Glad to hear that. Bob is very responsive. Did the lightening do a lot of damage?

Ed K5YZW · June 2020

Again I appreciate all the help. I got my SPE back from Bob. He said I had over-driven it too many times. I have tried to be very careful to not over-drive the amp but it has happened, usually a result of a mistake, not pushing it. Bob strongly recommends using ALC with the Flex. Does anybody do that and how do I set it up?

Bob Needleman · June 2020

Ed - all solid state amps running MOSFETs are much more sensitive to over-driving vs. tube amps. So you must insure you don't over drive them, and best way to do that is using ALC. The procedure for proper adjustment of the ALC should be in your amp's manual, but the basic idea is to set the ALC level to the point where your rated PO Max (eg. 1.5 KW) just drops off which will insure you never drive it beyond that point. The other way to do that is by setting the Max TX PO on the exciter (ie. the Flex) to the TX PO setting that will give you slightly lower PO from the amp (or even a bit lower to play safe). Remember that your signal really isn't going to be received much stronger if you go from around 1KW to 1.5KW, so keeping the power down under the max. rating of the amp will protect those expensive MOSET finals.

Bob K3AC

KD0RC · June 2020

Hi Ed, I discovered DDUtil when I was researching the Elecraft KPA500. It lets me set max RF out of the Flex per band and op/stdby. So for example, on 20 M, I can have a standby amount of 100 and an operate amount of 24. This has kept me from accidentally transmitting 100 W into the input of the amp. This utility also lets me control the amp and tuner from the computer. It also "follows" the Flex frequency, so tuner and amp band settings happen automagically without relying on RF sensing. It is cool (and reassuring) to hear the tuner relays click as I tune the Flex up and down the band or if I change bands. You might want to check into it to see if it works for your amp. 73, Len, KD0RC

KD0RC · June 2020

P.S. I also set up a .bat file that starts SSDR, and then opens DDUtil, my logger and SliceMaster. That way I won't forget DDUtil, defeating the whole purpose for having it... Len

DV · June 2020

All the Expert amps have a way you can set the maximum drive power. The amp will then talk to the Flex to make sure the Flex does not go beyond your set level. The procedure can easily be set up from the front panel. From the operate mode just press one of the arrow keys and the exciter limit power will pop up and can be set with the arrow keys. I'm not sure if this in the manual, since I had to remind Bob that that feature existed. Also, the Flex itself can control the maximum drive by using the TX Settings for the bands you use. I think this is a better way to protect the amp since using ALC can cause other issues.

Patrick · June 2020

Definitely the best way to go with SPE amps. I also use the SPE control app, and the cable built by Dan Tassell, KC5PCB. Well worth the cost, it is well designed and built. Connecting with this cable and USB cable direct to the computer and the USB from Dan’s cable to the Radio, gives very seamless control of the operation, power limits and direct frequency control to the amp and control app. Setting up the power limits from the front panel is fine. But having direct access via the computer app, gives real-time control of the power settings. Also, the radio, on and off controls the amps on and off. Dan, also provides proper voltage for the on/off switching using a small DC to DC conversion chip.

Keying Expert 1.5K-FA amp

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