Trimble ThunderBolt Assistance

[VK3QI]

Hi,

I have a number of Trimble Thunderbolt GPS working in various pieces of equipment - all successfully monitored by the VK4GHZ display and/or the TBOLT software on a laptop.

However, I have also inherited two Thunderbolt units which appear to be working correctly as far as receiving and disciplining is concerned, but fail to send any data via the RS232 port. Using the TBOLT software on a laptop as well as the VK4GHZ display, it is obvious that the serial data is not being sent or received (and a factory reset cannot be performed). Serial port is set at the default 9600,N,8,1

Does anyone have any experience in trouble shooting the circuitry of a Thunderbolt GPS? I have searched far and wide for the actual circuit diagrams but to no avail.

The firmware on one is 3.00 and the other 2.5??

Cheers
Peter VK3QI

[VK4GHZ]

Hi Peter

Have you looked at the RS232 serial out on a digital storage CRO?

Are you seeing any pulses swinging between +/- 10V at all?
What do you see?

(We assume the -12V rail going to the ThunderBolt is present.)

Haven't had the lid off my T'Bolt for years, but can you bus back from the DB9?
I would expect to find an RS232 level translator chip (similar to a MAX232 etc).
Does the +12 and -12 appear there?
TTL level signal going into the level translator look OK?

[VK3QI]

Adam,

I'll try and have a look at your suggestions at the weekend.

I had a cursory look yesterday, but couldn't trace the lead from pin 2 or 3 on the DB9 socket. I presume the tracks run under the enamel on both surfaces, as there is no obvious track on both sides of the board.

Thanks

Cheers

Peter VK3QI

[VK3QI]

Adam,

I did all the tests you suggested and everything appeared to be working normally on both units.

That made me suspicious that there was something else at play. I was using a separate switchmode supply and I discovered that if I connected the metal case of the thunderbolt to the earth of the switchmode supply (metal case type), the DB2/DB5 error stopped occurring on the display unit. The common of the power supply is connected correctly to the thunderbolt power plug, so the correct voltages are present, but clearly there is some earthing issue that I can't identify.

Anyway, both are now working AOK, both on the GHZ display and via TBoltMon on my laptop. If I get the chance I will test out with one of the plastic case switchmode supplies and see if the same effect occurs.

Thanks for the suggestions - that certainly convinced me that the Thunderbolts were not at fault!

Cheers

Peter VK3QI