Batboard

NEWBIE ALERT>> Hi everyone. I recieved an older vhf Syntor that has a 8 channel selector and a scan head. I am hooking it up in my shack. Everything works perfect except that it only will xmit across the room. It won't even register on my watt meter. I hooked it up just like it was in the vehicle. Does anyone know what the input ptt reference voltage should be? It is 12 volts now and stays the same when keyed. The input ptt is 12 volts and cuts to under a half volt when keyed. This doesn't seem normal but I don't know Syntors either. I am starting to think the final section is blown or something. It transmits on all the frequencies. I have great audio on my portable an all channels. What's t the deal?

Ok, lets trouble shoot this out. You have the orange and green power wires from the control head connected to power? The main red lead is connected to power, and all fuses are good?

The PTT reference line on the Syntor X is fed by the supply voltage on the orange wire, i found this out when i did my repeater conversion article on them which is over on the RBTIP website. The PTT is closed to ground when you transmit, so that's why the PTT line voltage drops. That's all normal so far.

The green wire powers the control head and the rest of the radio circuitry, it's also known as the ignition sense. Since it's working fine otherwise, receiving and so on, then that connection is fine.

It sounds like you have a problem with the main B+ feed, the large red wire, check the fuse, and pop the top cover off and check for voltage on pin A which is the main B+. It sounds like the radio is working but the PA is not receiving power.

If your radio is a high power drawer, it can eat over 30 amps. How good is your bench power supply? Be careful, many supplies like Astrons only tell you the peak current rating on the front, not the sustained current capability. Your description of the voltage drop sounds like the power supply cannot keep up with the current demand when you Tx.

I have a 1000 amp battery with a 30 amp supply to charge it. I have put my other syntor x on it and I get 100+ watts out of that one. Still seems like the pa still isnt recieving power I am checking the red and green wires now..

Another thing to check, if it has been a really long time since it has been used, is the pins on the main connector. I use a small art eraser, the pencil type that you can sharpen in a pencil sharpener, then i trim it down a bit more at the tip so it fits between the pins.

If you have a continuity check on your voltmeter than check continuity from the main red B+ lead to the pin labeled as "A" on the top side of the board where the main connector J1 is soldered to it, and then from that point check continuity from pin "A" to the power connection in the PA section.

You must have a bad connection somewhere and the PA is not receiving power. If the red lead has one of those large Motorola fuse holders in it take that apart and clean everything, they corrode after a while inside. I have had some that were totally filled with powder, corrosion.

I checked all the connections. All the connections are making it to the radio good continuity all through. I checked the voltages that the x model control head has and it matches up with the older syntor on the ptt pins. I wonder if the guy that took out of the truck shorted something out when he disconnected it. I might just box it up and use it for a reciever in a repeater set-up later down the road. It is really clean on the recieve end..

One last thing you can check, turn the radio off and remove the bottom cover, power it up, and check for voltage at the PA. Back left side you will see all the feedthrough pins and the large red and black going to the PA.

Just make sure the voltage there matches the supply voltage. If it does then flip the radio over and check the voltage on the other side of that feedthrough. I had one with a cracked solder joint that was intermittent, and one that was just plain bad, broken.

I'm no expert, but don't overlook the fact that some smart-a** might have gone into RSS and turned the output power down to zero. Everything would work great except no significant output power.

You can do this on MaxTracs and Spectras, so why not Syntors?

Bob M.

Syntor X's are not RSS programmable they use a memory module with an EEprom, or a Prom on the older versions.

Also the power is not programmable, it's set with a trim pot on the common circuits board.

The X9000 is the same way, not a soft pot value.

I'm no expert, but don't overlook the fact that some smart-a** might have gone into RSS and turned the output power down to zero. Everything would work great except no significant output power.

You can do this on MaxTracs and Spectras, so why not Syntors?

Um, because there isn't an RSS for Syntors. They have a bipolor prom for frequencies, PL, DPL etc & use the R1801 for programming. Alignments are done manually by techs.

Sorry Bob, just couldn't resist the jab.

Darn!! kb0nly beat me too it!

Another thing to try, if you have an ammeter put it inline with the red wire and see how much if any current flows while in transmit. If it's still pulling a significant amount of current but not producing output check the power output trim pot on the common circuits board.

DJP126 wrote:

I'm no expert, but don't overlook the fact that some smart-a** might have gone into RSS and turned the output power down to zero. Everything would work great except no significant output power.

You can do this on MaxTracs and Spectras, so why not Syntors?

Um, because there isn't an RSS for Syntors. They have a bipolor prom for frequencies, PL, DPL etc & use the R1801 for programming. Alignments are done manually by techs.

Sorry Bob, just couldn't resist the jab.

Darn!! kb0nly beat me too it!

Yep, got there right before you did.

And a stab at you, only the original Syntors and very early Syntor X's used the Prom, the later Syntor X's have the orange label memory module with an EEprom in them. Easy to program!

kb0nly wrote:

DJP126 wrote:

I'm no expert, but don't overlook the fact that some smart-a** might have gone into RSS and turned the output power down to zero. Everything would work great except no significant output power.

You can do this on MaxTracs and Spectras, so why not Syntors?

Um, because there isn't an RSS for Syntors. They have a bipolor prom for frequencies, PL, DPL etc & use the R1801 for programming. Alignments are done manually by techs.

Sorry Bob, just couldn't resist the jab.

Darn!! kb0nly beat me too it!

Yep, got there right before you did.

And a stab at you, only the original Syntors and very early Syntor X's used the Prom, the later Syntor X's have the orange label memory module with an EEprom in them. Easy to program!

Yeah, a little bonus for those that figured out how to do it. The EEPROM was still designed to use the R1801 with the RTL5815 adaptor.

I have only seen one Syntor X so far with the older white label memory module with the Prom. I think a lot of them were replaced as the radio needed to be reprogrammed and not many of them survived.

I saw an R1801 on ebay a few weeks back, i wonder what that sold for.

A tad bit of history for you. The original proms for the syntor, syntor x, mcx100, mx300s, etc. were manufactured by MMI (Monolithic Memories, Inc.) out of California. They ran into a problem with the EPA & from what I was told, went bankrupt paying for the clean up of their problem. Some little company called AMD bought the site & continued the clean up.
Due to these problems, the bipolar proms quickly became NLA. Motorola had to :
1) find a direct pin for pin replacement for each device used.
2) rewrite all of the R1801 apps involved.
3) design & manufacture new adaptor modules for the replacement proms to be programmed by the R1801.

This was a very busy time for us in the Test Equipment Depot. Especially the guy that took care of the 1801 (me).

Ahh, so that's what forced the change.

Motorola only makes a change when forced to it seems.

Thanks guys. Does anyone know where I can get a schematic of this radio? Nothing is marked on the boards..

You would have to get a service manual for it. If you have access to a X9000 service manual the PA and RF sections of the radio are the same. The only differences are the common circuits board and the personality board.

I just got a X9000 VHF Service manual, i might be able to find info for you from that if i have time to.

Cool. It would be nice to know whats what..

If nothing else when i get some spare time tonight or tomorrow i can scan the PA schematics that will at least give you something to go on. It sounds like the radio is working fine otherwise.

Thanks you have been great!!

Scott, If I'm understanding him right, he is working on a Syntor, not a Syntor X. If so, the PA, as well as everything else, would be completely different.

Sparky, one other thing you could check, especially if it is drawing 'normal' current durring TX, is the TX/RX switch. If it isn't receiving voltage on the DC terminals of it on transmit, the output from the PA won't get connected to the antenna port. It's also possible, although doubtful, that the TX/RX switch itself may be bad. In either case, it would probably still receive properly as the switch is a pair of reed switches.

It doesnt draw the voltmeter down when I transmit. I am trying to check it but I dont want to start probing around blindly.