SPE/Flex 6xxx drive control

Rick Ciotti W3DIY

The LDMOS failed in my SPE1.5K. There were numerous unexplained overdrive errors in the SPE log. The Flex drive power is set to 10W on all bands. I notified Bob H of the errors, prior to the total failure, but he did not have an explanation. My question...could this be a fault with the Flex6600M, there is no ALC connection the drive is controlled by the SPE firmware.

Pat N6PAT

Jon_KF2E

Bill -VA3WTB

Richy

Mike-VA3MW

Just about all current amps have overdrive protection and then shutdown the amp.  I would find it hard to think an overdrive issue caused this.

Since I am involved in another amp (non-FRS) project that has had its share of failures with no explanation and I am starting to believe that the BLF189's (in this case) just **** up on their own.  They are not impervious to failure even though we wish they are.  We have seen the LMDOS supplier actually replace the LMDSO's at no cost.

In the case of SPE, they should reach out to their LMDOS supplier and talk to them about it.

Mike 

Rick Ciotti W3DIY

Thanks! The 6600M profiles have always been set to 10W on all bands. At this drive level the SPE output is about 1KW.  BUT the SPE overrides the programmed values. As I change the SPE drive control the 6600M Tx profile changes.

Rick Ciotti W3DIY

It goes into standby mode but can still take out a LDMOS.

Jon_KF2E

Rick, I wasn't referring to the setting in Profiles. There is a setting on the TX Tab of Radio setup that has Max Power. It will(supposedly) not allow the radio to transmit above that setting. It will also restrict third party apps from trying to transmit at a higher setting.I set mine to 35 watts to protect my Yaesu Quadra.

73, Jon...kf2e

Mike N9NTC

Are you using the Interfacing cable from Dam Tassell KC5PCB. If you are set the power for each band from the SPE Amp. the Flex will not exceed the input power usually 5 to 10 watts. I use the SPE 1.3 and works well and can't accidently overdrive the amp.

Clay N9IO

Jon KF2E, Thats how I have my 6600 set is at 30 watts max to drive my 2KFA. No issues quite flawless. In the TX of the menu.

Rick Ciotti W3DIY

Yes I am using KC5PCB's cables.
 The SPE's drive power has always been set to 10W on all bands. No need for maximum output with the present band conditions. I assumed it would be impossible to overdrive the amp with these settings yet there were 9 overdrive events in the log. 

Rick Ciotti W3DIY

Occasionally run barefoot so the max power was 100W. Until I get to the root cause I will set the max power to 10W.

Bill -VA3WTB

It seems that the over drive is not from the Flex then as you have everything set correctly. I have also read in other forums people having the same problems using other types of radios as well. It seems to be SPE 1.5K issue.

Jay Nation

Pat N6PAT

The max power out for Flex radios is 100 so 1% = 1 watt, 2% = 2 watts ,etc.

Bill -VA3WTB

I believe Pat is right. 50% on the slider should be 50w.

Rick Ciotti W3DIY

Update...I was informed by the US SPE dealer, Bob Hardie W5UQ, that this is a known glitch with the Flex software. Unfortunately I was unaware of this when I made the SPE purchase. The workaround is resetting the 6600M Tx delay. Anyone know what that value should be?

Mike-VA3MW

Rick, can you explain more on what the Glitch is that is a Flex issue?  Have we acknowledged that?  Any details you have will be appreciated so we can make sure the details are correct.  

Rick Ciotti W3DIY

Michael, it was explained that the Flex drive power can spike unexpectedly, causing an overdrive condition, and was informed that the SPE will go into standby when this occurs. I realize the sequence of events that trigger the spike would be helpful, but I'm reluctant to risk taking out another LDMOS to reproduce this condition.

Doug

Clay N9IO

Same here like the NAQPs I leave the amp off and set max TX power back to 100. That setting you can rely on the profiles I have found you cannot. No idea why I only know I cannot trust the profiles.

Alan

I am not an expert, or even a novice when it comes to RF engineering.  However, I have 40 years of experience in converting volts and amps to thermal power and dissipating the thermal power to the environment.

So if there is an overshoot from the Flex that is harming the amplifier's transistors, is it thermal overload or something else, like high voltage that breaks down the transistor junctions?

If it is thermal, it takes amps, volts AND time to produce and dissipate thermal energy, resulting in an increased transfer of heat to the environment, thus, a higher delta T to drive the watts to the heat sink. (temperature).  A "spike" doesn't seem like a large unit of time to drive such a thermal outcome?  Do any transistor experts out there care to comment?

However, there could be a harmful amount of voltage (not time-dependent), but other factors seem to be at play for that to occur, such as feedline and antenna characteristics.  (outside my wheelhouse of knowledge, but know it is out there).


Just asking.

Alan
WA9WUD

Bill -VA3WTB

Alan, I think in theory your correct. In the case of a Flex, they have been well known for rock solid TX power control. But there have been rare cases when people have had over power problems, but for most, it has not been a problem.

In the case of over shooting people claim to see on their SPE 1.5 amps it does not make any sense at all that it is software related. If it is then all Flex radios would be overshooting but they are not. Mine does not.

If it were my amp, I would go after the company and ask why the amp allowed damage from over power if their is any.

Alan

Agree.  I have followed the issue of the Flex power setting exceeding the recommended excitation level for the amp. (due to operator error or not paying attention to changes the Flex makes to your TX profile).

Under the power setting scenario, it seems reasonable that the thermal limits of the transistors of the amplifier could be exceeded with typical transmission lengths (especially FT8), but then again, with these modern, microcomputer-controlled amps, it seems like the amp would protect the power transistors before failure.

Not buying the "spike" scenario when it comes to a thermal overload of the amps power transistor unless it is a high voltage induced breakdown of the transistor junctions.  I would not blame the Flex for high voltages on the feedline.

Alan

Alan

I put some math behind my thoughts to bracket in the idea:

The manual for my Palstar amp says it can detect the incoming RF, determine the frequency, then close the output relay, then the input relay: all in 20.5 milliseconds.  Let's assume this is typical of the modern amp's time to detect an overexcitation and shut itself down.  I will use 25 milliseconds (25E-3) in my math.   Even if the amp does not shut down automatically, 25 milliseconds seems a reasonable period for a "spike" given that the middle of the audio spectrum is 2KHZ (presumably the source of the SSB overexcitation), the period of the over-excitation (2KHZ) is 0.5 milliseconds, much less then the conservative value used in my math.

Next, I will select a high overpower condition that we can all agree on as being the highest possible.  I will use 5,000 watts (5E+3).

Now, convert the thermal energy equivalent of  5E+3 watts for 25E-3 seconds to continuous watts for one minute; gives 2-watts thermal equivalent.

Alan
WA9WUD

PS. I have too much time on my hands today.

Rick Ciotti W3DIY

The SPE just flagged an overdrive alarm on 40M. The 6600M max Tx power was set to 20W, the SPE drive power set to 15W. With the SPE ATU active the SWR was reading 1:1,the Flex SWR is hardly noticeable. BUT on this freq. the antenna SWR is about 3:1. I have changed the 6600M to 12W max and the SPE to 10W. More tests ahead.

Alan

I did not purchase the SPE, but read the manual as part of my decision prior to making a decision.

As I recall, in the manual, it stated that operation with feedline SWR greater than 3.0, before tuning, required a de-rate.....not for thermal reasons, but on reasons for the potential of damaging high voltages within the internal tuner.

Or....am I mixing this up with the Elecraft Amp....my memory is not so good.  It's in one or the other, but the concept is the same.

I do not have a resonate antenna, so this was a non-starter for me.

Alan

Bill -VA3WTB

Glad I didn't buy an SPE amp. looking back at all the comments over several weeks most problems people are having are with the 1.5 amp. Very few if any are having this problem with other amps.

Because of this discussion I'm sure Flex is running test as we write here.

Rick Ciotti W3DIY

Rick Ciotti W3DIY

According to the SPE dealer there are many Flex owners with this amp who have no issues. The reason I posted here was to locate a few of those happy owners.