RM Italy KL7505v Overheating Protection problem.......H E L P!!!!

[Juan Fernandez]

73's my friends. I have a 7505v and i have the Temp shutdown problem. I only use it on SSB and I can't talk more than 2min and it will go on protection mode (TX LED BLINKING) the funny thing is that the amp is not even hot. I contact the company I got it from and they send me a replacement and is doing the same exact thing. It will do it with 3 different radios, 2 antennas with different coax, even with antenna tuner and dummy load. My SWR is lower than 1.2 with the AMP. The fans are working, when unit is ON they are on slow speed and when i transmit they speed up, they also stay on HI speed when the Overheating Protection mode is on and I have to turn the AMP OFF /ON to reset. Is there anything I can do to prevent the overheating protection to do what is doing, maybe re-calibrate or adjust the temp shutdown. H E L P !!!!!!!! Thanks

 

[Handy Andy]

 

[Eldorado828]

Andy, so it won't work correctly until it's modified?

 

[Handy Andy]

Well, go to search, you'll find the thing has a 11-meter "block" - someone in this thread set us straight earlier in another post about this - the Vid shows two "holes" needing a solder jumper - this bypasses the Hi-SWR block the amp uses in it's filters to generate the "overheat" condition.

Applies to both... 740X and 750X

I'd try the jumper mod to see if it removes the condition - especially since they've swapped the amp 2X with the Dealer - may he got back the same one - but remember the issue of "Break the Seal - you own it" so if you can't make it work in it's STOCK form, you need to know that your efforts will void the Warranty - so is it worth it?

The choice is up to the operator...

 

[CB590]

Andy, so it won't work correctly until it's modified?

Correct. There are two holes that need to be jumped together behind the face plate to run 11m (CB). SimonTheWizard has a video up on it. This is not like the little RM203 that you can just plug in and go. The 7405/7505 were made to meet FCC guidelines for use in the USA hence the "block" of 11m band.

 

[Slowmover]

Mine has the mod.

 

[Handy Andy]

 

[Mudfoot]

mine trips with/without mod

 

[Juan Fernandez]

I have the mod done and they didn’t sent me the same amp because I have both amps with me. The amp is NOT overheating, I remove the front face plate where the mod is done and if I operate the amp with the facebplate off I can talk for hours and no overheating protection. Install the front face plate back and not even transmit and the TX blinking LED is back, temove the front face plate and I can use the amp for hours and no false overheating protection.

 

[2NC995]

Sounds like something is shorted to the case when the front panel is installed.

 

[Handy Andy]

!!! Remember - we are not posting this to tell you how to run your life - we're trying to help you !!!

Uh, were you aware that one of the reasons why the Hi-SWR 11-meter block was put in place right?

How many watts are you running into the amp?

For if you think that is set up for High Drive, sorry no - because it's a low (INPUT) drive amp, but part of the jumper situation was to attenuate any spurries - so the amp may be fine now, you're not telling us how many watts you are driving it with...

​

There looks to be a current sensor (for draw when voltage sags - it's triggers this alert too from Regulation) so if you have issues with overdriving the amp - remember when you install the jumper - you're bypassing part of the filter network - so if you push too hard, she'll trip.

Also = your running SSB into an amp that biased for AM/FM/CW - but possible for SSB...

Were you aware of this...

You said SSB - Needs Class AB bias have you set up the amp for it?​

When you run open cover, it tells me that you can also reposition the ribbon cable - so if the amp seems to run ok, remember in the vid he says that you can use it without the cable - so something tells me the cable is bad, or your front panel isn't "bonding" to the case for shielding.(have you tried to see if the cable is properly oriented and fully seated - thinking there may be problems with the cable communication or open lines not going anywhere- which does cause RF issues with any amp)

So to see two amps this way though, tells me something's wrong but I'm not sure what to give you in guidance to solve this.


Either way - too much RF INPUT energy the thing will trip

 

[Arizona8255]

73's my friends. I have a 7505v and i have the Temp shutdown problem. I only use it on SSB and I can't talk more than 2min and it will go on protection mode (TX LED BLINKING) the funny thing is that the amp is not even hot. I contact the company I got it from and they send me a replacement and is doing the same exact thing. It will do it with 3 different radios, 2 antennas with different coax, even with antenna tuner and dummy load. My SWR is lower than 1.2 with the AMP. The fans are working, when unit is ON they are on slow speed and when i transmit they speed up, they also stay on HI speed when the Overheating Protection mode is on and I have to turn the AMP OFF /ON to reset. Is there anything I can do to prevent the overheating protection to do what is doing, maybe re-calibrate or adjust the temp shutdown. H E L P !!!!!!!! Thanks

73's my friends. I have a 7505v and i have the Temp shutdown problem. I only use it on SSB and I can't talk more than 2min and it will go on protection mode (TX LED BLINKING) the funny thing is that the amp is not even hot. I contact the company I got it from and they send me a replacement and is doing the same exact thing. It will do it with 3 different radios, 2 antennas with different coax, even with antenna tuner and dummy load. My SWR is lower than 1.2 with the AMP. The fans are working, when unit is ON they are on slow speed and when i transmit they speed up, they also stay on HI speed when the Overheating Protection mode is on and I have to turn the AMP OFF /ON to reset. Is there anything I can do to prevent the overheating protection to do what is doing, maybe re-calibrate or adjust the temp shutdown. H E L P !!!!!!!! Thanks

Hello Juan Fernandez,

I recently bought a very lightly used KL7505 from a guy I met on the radio and found that it also had the same exact problem that you described.
I searched the Internet and was able to find a complete and accurate set of schematics for the KL7505. I found that the amp has two separate temperature sensors. One is a Si diode that is thermally tied to one of the RF Power transistors and the other is a very tiny, surface mounted Thermister R7 that's on the small PIC microcontroller PCB that's located behind the control panel. This is the sensor that is intended to monitor the ambient temperature of the amplifier's surrounding. The problem is that the designers located the sensor inside the fully enclosed interior of the box where it is not only unable to measure the temperature of the surrounding room but, it's (stupidly) measuring the much warmer interior of the box. What do you think is going to happen? That's right, the computer will think the ambient temperature in your radio room is very warm and place the amp into over-temp. shutdown mode.
The solution I arrived at was to temporarilly open the little control panel in order to expose the sensor to actual room temperature. This made the over-temp shutdowns disappear, thus proving my idea was correct.
The permanent solution was to drill a series of six small holes through the bottom metal cover plate positioned so the holes are below the small space in front of the CPU card. Then I cut a 30mm hole and mounting holes to mount a small computer 12V fan onto the bottom cover plate, located in a spot behind the CPU PCB. I tied the tine fan to a constant source of 12V inside the KL7505. This then forced exterior ambient air to flow over the small CPU PCB such that the surface mounted temperature sensor is now able to measure the actual room temperature. The shutdowns never happened again. I'm sure that if I ever tried to operate the KL7505 in a very warm room that the unit will go into shutdown because now, the surface mounted sensor is able to measure the temperature of the actual room temp. as it was intended to do by the designer. Now I use this amp all the time and I love it.

Good luck.

 

[Arizona8255]

Well, go to search, you'll find the thing has a 11-meter "block" - someone in this thread set us straight earlier in another post about this - the Vid shows two "holes" needing a solder jumper - this bypasses the Hi-SWR block the amp uses in it's filters to generate the "overheat" condition.

Applies to both... 740X and 750X

I'd try the jumper mod to see if it removes the condition - especially since they've swapped the amp 2X with the Dealer - may he got back the same one - but remember the issue of "Break the Seal - you own it" so if you can't make it work in it's STOCK form, you need to know that your efforts will void the Warranty - so is it worth it?

The choice is up to the operator...

The thing is Andy, the KL7505 isn't really overheating at all when it goes into the shutdown mode. It's because the cabinet isn't ventilated and the Ambient Room Temperature sensor, R7 is located INSIDE rather than outside of the warm cabinet. Just make sure the ambient temp. sensor is able to measure the room temp. rather than the cabinet interior and the problem will disappear. Drill some holes in the bottom plate and provide a tiny fan to force room air to flow over the CPU card (where the ambient sensor is) and the design will function as intended.

 

[Handy Andy]

Oh this is awesome!

So the previous poster did not read the manual which would have saved a lot of speculation on our part.

The posts I did above were to guide the OP or anyone following - to do the "jumper mod" which is part of the band expansion "kit" demonstrated in the vid link above.

The rest of problem then lies in power from the Regulator and it's ambient temp sensor too close to the main power devices forcing you to modify the case in order to blow more air in to fool the sensor?

Hey? Where were those links to this thing located?

 

[Arizona8255]

Oh this is awesome!

So the previous poster did not read the manual which would have saved a lot of speculation on our part.

The posts I did above were to guide the OP or anyone following - to do the "jumper mod" which is part of the band expansion "kit" demonstrated in the vid link above.

The rest of problem then lies in power from the Regulator and it's ambient temp sensor too close to the main power devices forcing you to modify the case in order to blow more air in to fool the sensor?

Hey? Where were those links to this thing located?

Hi Andy, It's not anything about power from the regulator. It's that the designers don't want the amp to be used in a room with a high ambient temperature and that's what the little owner's manual says is the reason the amp will go into this mode. It's not because the amp is overheating. It's because your room is too warm. The little fan that I added isn't for the purpose of cooling anything that is excessively warm. It's only to apply ambient air to the surface mounted sensor so it can do what the designer wanted it to do. Apparently they had a design team and the person who mechanically designed the amp either overlooked or misunderstood this concept and didn't realize that the firmware needed to know the Exterior rather than the Interior temperature.
I don't remember the links where I found the schematics but I saved them as PDFs so just do lots of searches like KL7505 pdf and they'll show up. There's one called Operating manual but it's actually the schematics of the small computer card showing the Thermistor sensor, R7 that has been misplaced. I have attached that PDF in a subsequent posting. You can see how tiny R7 is and how ridiculous is was to use a surface mounted sensor because it can't measure the exterior temperature very well where it is. Someone at RM Italy sure was confused.