ALS500 Mobile Amplifier Issues
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- Опубліковано 17 жов 2024
- The ALS500 amplifier has two significant issues that are easy to correct.
The ALS500 with remote jacks has what are essentially unfused small wires exiting on remote jacks. Because current is not limited to safe values for wire size, remote wires can become red hot. It is fairly easy to prevent this.
While into the amplifier, it is best to inspect all of the solder connections. This is especially true on the high current leads and the rear power connector.
The second issue is mainly when PP100 transistors are used in place of 2SC2879 transistors. The amplifier has a large current spike. The PP100's have a lower base bias threshold, typically I measure around .51 volts or so, and high dc current gain at idle. The bias circuit has a very brief (a few milliseconds) spike of around .75 volts before it settles to operating bias levels. The PP100's also have a good bit more VHF gain. This causes the amplifier to momentarily oscillate upon relay closure.
The momentary oscillation causes a very large current drain from the high current 12V supply, near 100 amperes and more.
If a 12Vdc current protected power supply is being used, this spike can cause overload or foldback circuits to trip. This oscillation also can cause random unexplained "Fault" trips of the amplifier protection circuits. It seems reasonable to expect this will also shorten PA transistor life.
Both of these issues, the unfused leads and the oscillation and bias surge, are easy to correct. While correcting these problems soldering and lead dress should also be inspected and corrected!
I have a kit that will will correct the bias and safety problems.
Hi Tom - How do I purchase the "board you have that will fix this ?" Thanks for sharing your knowledge with us ! BTW - your troubleshooting tips for the AL-572 were very helpful converting mine to GI-7b's.
I lost one RJ45 socket and blew part of a trace, so I fused it. They took the cheap way in their placement and mounting. If memory is right there was room for a sub assembly board. I also went to shielded Cat 6 cable. Mine has been running mobile for about 10 years in an H3 Hummer, so it's had it's share of off-road use. I recently went thru it and also some bad solder joints to the power plug. Their soldering is a little undesirable....I'm trying to be kind here.
I found your video while researching an issue I'm having with a new ALS-500M. Powered by the Ameritron SPS-75MV, its meter registers nothing at any power setting, on any band, when the IC-7300 is keyed, even though the ALS relay clicks clearly. Any ideas? I would be most grateful.
Hi so you have the board available for sale ???how can I get in touch with you ?
How do I get in touch with you I have a this problem please
How can they let these amps go on the market like this?
Man every time I look up an amp you got a lot of info on it
Saw your Video I have an ALS500 and was new 1 year or so....when I attempted to use remote on off and band changing would trip Fault immediately I can only use band switching....so what's your fix ?
AC4KW
Hi, I saw your comment and had this same issue. I had it sent to MFJ before they shut their doors and it was a known issue for some of the ARI-500s when rf is sent through with it on. The green wire attached to board nearest the fan with 2 torrents attached is what the tech disconnected. And works great now
I have this problem, too. Is there a potential fix for purchase??
-K7RXT
I have to redo the bias/control board, but for now, we have a patch board that is simple to add. The heatsink is difficult, however. I don't know what they were thinking when they changed to that heatsink or who changed it!
It’s just so absurd, and annoying to say the least. Just a terrible, albeit expensive product. And 9/10 times it shoots swr high, makes it go into load fault.
@@andrewturner2615 The issue with the control board is it was designed around 2SC2879s which behave differently than the PP100s used now. MFJ never corrected the control board. I called them a few times about issues and offered a fix, but the people there said it was fine and did not have a problem.
So it is up to the customer to fix the amplifier.
Sometimes the spike is so bad it will actually knock the PP100 transistors out.
@@Jerrythenerdful I thought I had replied last night, and don’t see my comment. I had done some research after seeing your video initially. It’s quite an intricate process I can see to remove and change the transistors, if that’s even a fix. I would like to learn more if we can exchange information and be able to purchase a fix directly from you when it’s fully available. It is so disheartening to purchase such an expensive item, with the RC and the band changing interface(which faults instantly every key up) to find it as a weight in the back of my truck. Ameri-MFJ really should be held liable for such a poor product. And this whole time I thought it was my coax or antenna or operator error. Super frustrating. Though, very good video and informative, and if there is someway to get a fix from you, a nice consideration would be in exchange. Thanks in advance, and 73 de
K7RXT
@@andrewturner2615 I made several attempts to get them a fix for this, but some tech insisted they do not have a problem. The entire remote interface system has a few design problems but those are not showstoppers. The big field issues are the very sloppy assembly, the anodized heatsink, the unfused 12V leads on the CAT cable, and the bias spike that shows with the PP100 transistors (sometimes triggering them into oscillation). All of this is field fixable but at hundreds of dollars cost.
It would only be a few dollars extra cost done at assembly, but that won't happen.
Nicely done as always Tom!
Good video Tom, You are still the best
What is the board that you made to correct this?
We have been so busy I have not had time to list them yet. I'll try to get some instructions written and put them up. Are you having issues damaging transistors or having the amp trip off when you key the amplifier?