FE5650A CPOM - Page 1
Forum section: electronics / repair

author: Cyclotron
author_rank: Unknown
timestamp: September 09, 2024, 01:22:06 am
content: I picked up this FE5650a Option CPOM after sending an low offer and being surprised when it was accepted.https://www.prc68.com/I/FEIFS.shtmlThe pinouts on this site appear to be correct. I've connected Termite (serial terminal software) and a TTL adapter (I've tried more than one) to the serial pins. I've swapped the TX/RX as that has gotten me in past.This unit is setup for 15Mhz and I want to change it to 10Mhz.There appears to be load level chip or something between the DS80C323 and serial port (seen in photo attached). I've tried 9600 baud and 9950 per some stuff I've seen.I can probe and see stuff headed into the unit but nothing seems to come back.I have considered removing the 8-pin chip on the UART pins and replacing it with a MAX232, as is found on other variants of this oscillator.Anyone with hints would be greatly appreciated!

author: perieanuo
author_rank: Frequent Contributor
timestamp: September 09, 2024, 09:50:41 am
content: hi, remove u412 and connect ttl adapter and test. maybe u412 connects to some mcu and your comm is affected.converting from ttl to rs232, why?

author: Cyclotron
author_rank: Unknown
timestamp: September 09, 2024, 10:49:08 am
content: Quote from: perieanuo on September 09, 2024, 09:50:41 amHmm,I did test the pins out on u412. Pins 2 and 3 are connecting to the db9 serial connector on wires gray and white. Pins 1, 4, and 7 connected to ground.Pins 5 and 6 to the DS80C323 and I just realized I didn't trace pin 8. And, the path between pins 2 and 3 may be intercepted as didn't review the path end to end.As to why covert to RS232, I don't have a good reason other than what is there isn't working, the pad is available and other units such as this with different options have the MAX232 chip installed. Yeah, not good reasons.You gave me a couple of ideas and I'll try that. I don't recall probing the traces between the small chip and the DS80C323 microcontroller.And removing this small chip isn't a bit deal and I can tap right onto the pads for TTL.

author: perieanuo
author_rank: Frequent Contributor
timestamp: September 09, 2024, 12:06:33 pm
content: sometimes transceiver are just dead.of course pay attention to ttl level, interfacing to ds directly may be dangerous.pin 8 cts maybe is irrelevant viewing you have a 8-pin transceivr make me think rx/tx is enough to talk to ds chip

author: Cyclotron
author_rank: Unknown
timestamp: September 09, 2024, 07:50:48 pm
content: Quote from: perieanuo on September 09, 2024, 12:06:33 pmI'm working to identify that 8 pin chip as I'd like to see a datasheet on it. The letters on it aren't coming up with anything that I can find so far.

author: perieanuo
author_rank: Frequent Contributor
timestamp: September 10, 2024, 11:33:26 am
content: must be something like max3314

author: Cyclotron
author_rank: Unknown
timestamp: September 10, 2024, 09:41:36 pm
content: I connected a TTL adapter directly to pins 5 and 7 on the DS80C323 and I do not see anything come back. So I'm guessing there's something else going on here. I'm going to post in metrology to see if anyone has experience with this unit and option.