HT1250 dead

[arlojanis]

I have a VHF HT1250 that appears to be dead. I have battery voltage on both sides of the off-on switch so it and the fuse must be good. I can not read the radio. What do I check next?

[Jim2121]

clean all the contacts from the radio to the pc, check the cable & pins...Last post that had the same problem had a cable problem & a some missing pins on the cable...
no errors? just can't read? for starters

[arlojanis]

The first problem is a dead radio. I tried the read just as a test. When the radio powers on, it will probably read.

[Jim2121]

The first problem is a dead radio. I tried the read just as a test. When the radio powers on, it will probably read.

Is this the same radio you posted on 7/2/2006? with the same problem? I did a search: HT1250 dead.... you got a reply to start probing... thats all you can do. Can you get a wattmeter? Another 1250 and see if it works? A fresh battery off the charger, not 1 that was charged and left on overnight... these are a few ideas. Unless you can get/test another radio!!
what firmware is it?

http://batboard.batlabs.com/viewtopic.p ... T1250+dead

[n1gtl]

If you know the fuse is good and the switch is good, could it be bricked? Can you trick it into a firmware update with a second HT1250? If it is "bricked" you can start a firmware update with a different radio and when you get to the point of removing and reconnecting the battery, switch to the bad radio.

[HLA]

did i miss something or did you ever state if the display is dead or what's on it or what error message is on it?

[arlojanis]

This is a different radio.
I am using a new battery.
If it is bricked, it bricked itself.
The display is blank.
No signs of life in the radio.

[arlojanis]

I just tried the reflash procedure and swapped radios at bootstrap time. I got the message "Failed to detect Flash ROM size". The green LED was on after this. Radio is still dead. Looks like another brick.

[Al]

Sounds like the uP isn't being clocked.....or it's being held at reset. Are you able to check for 16.8 Mhz at Y3761(that's the xtal near the backup battery holder)? You should also have 7.3728 Mhz at the uP U409 pin 90(EXTAL).

[arlojanis]

I connected a scope probe to the antenna jack of a service monitor, set the monitor for max sensitivity and touched the case of the 16.8 crystal in the dead radio and to a good radio and the monitor picked up no 16.8 signal from either.

[Al]

According to my schematic, the case on the XTAL is grounded, so I wouldn't expect you'd see anything there. If you're using a X10 scope probe, you should see 16.8 Mhz on pin 1 or 2 of the crystal.

[arlojanis]

Going thru the 16.8 oscillator test again, I got a signal from a good HT and no signal from the bad one. I subbed in a good SP50 crystal and still no oscillator. The crystal from the bad radio checks good in a crystal tester. So, I think the 16.8 is dead, but not a bad crystal.

[Al]

Unless you've subbed with an exact replacement xtal, I wouldn't depend on an SP50 crystal to oscillate reliably in the HT1250 circuit because of the differences in the crystal manufacturing specs like load capacitance, series resonant impedance, etc.
Before I declared the original XTAL good, I'd want to substitute with an exact replacement.

[hb001]

I seen this several times and there are a few more thing's I would check. Also, you said you tried an SP50 x-tal, don't know if that will work, due mostly to differences in part specs.

Here are other things you could check on your Ht1250
This is probably more in depth trouble-shooting requires tools and skills as well a schematic.
There are two 3.3v regs. One is easy if you check any of the tactile switches remembering one side is gnd and the other side should give you a 3.3v, that's your digital side and the analog side 3.3v reg is by the battery contacts. If your missing any of these voltages than it could be your Q400 mosfet or the regulator. If both check out good. Then I'll tried the actual e2prom, sometimes there's cold solder or it's just plain dead.

[911-EMT]

Can someone explain how to check U409 EXTAL= 7.3728 MHz? on ht1250 page 8-17 in detailed service manual

[Al]

You have to use a hot air rework station to remove the shield from the uP or ASFIC before you can get at pin 90 on the uP(EXTAL) or the SYN output of the ASFIC which supplies the 7.3 Mhz clock to the uP.
There are no test points where you can check outside of the shields.

[911-EMT]

Thanks Ai i have a tot air gun and i removed rf shields from this type of board in the past my question was on the test procedure to find the 7.37 mhz how is this done

[Al]

I'd look at pin 90 of the uP with a X10 scope probe to check the level and period(frequency) of the 7.3 Mhz clock.

[911-EMT]

Thanks Ai for the info i will use a r2600 analyzer with a X10 scope probe