HP8648C A10 Frequency Ext. Module Repair - Page 1
Forum section: electronics / repair

author: scopeman
author_rank: Frequent Contributor
timestamp: January 10, 2016, 01:31:00 am
content: Does anyone have any experience fixing the A10 (08648-60040) module used in the HP8648C (has option 1EA high output power)? It looks like the output amplifier IC/Hybrid is bad. This part is no longer available from HP and no released schematics exist.Is there anyone on the forum who has worked on these or perhaps can identify the amp chip used? The output amp bolts into place on the die cast housing on the module with four 2-56 allen head cap screw. There are only two electrical connections input and output to the amp.Any suggestions would be greatly appreciated.SamW3OHM

author: TerraHertz
author_rank: Super Contributor
timestamp: January 13, 2016, 09:21:51 am
content: Quote from: scopeman on January 10, 2016, 01:31:00 amYou might try contactinghttp://artekmanuals.com/and asking if they know of any service manual with schematics for that model.It doesn't show up in their online index, but you never know.I've have some luck with them, getting HP schematics that I didn't think were available.

author: rafik
author_rank: Contributor
timestamp: February 07, 2016, 12:24:33 am
content: Hello,I am new in the forum and I hope I can learn from you.Well, I have a HP8648C signal generator with serial number 3642U1637 but I don not count whit the service manual.Please somebody could me advise how to go out from the mode PULSE?, I tried of differents ways but nothing. This model has not options and connector "Pulse In" back, in the rear.In addition which manual cover this serial number?I hope you can give me a hand with this.Greetings to all.

author: IconicPCB
author_rank: Super Contributor
timestamp: February 07, 2016, 06:09:17 am
content: Tryhttp://bama.edebris.com/download/hp/8648/8648A-B-C-D-Signal-Generator-Operation-and-Service-Guide-08648-90048.pdf

author: rafik
author_rank: Contributor
timestamp: February 07, 2016, 05:44:22 pm
content: Hi,Thank you very much for your contribution.Well, it is right that I powered off the instrument before turned off pulse modulation. Now, According the service manual it is necessary to apply a TTL-high signal in the rear-panel PULSE IN connector, but there is a complication, my HP8648C version has not a rear-panel pulse in connector.Please, has somebody any ideas what to do?Thanks in advance for your help.Best regards

author: mmaseda
author_rank: Contributor
timestamp: November 05, 2017, 11:04:06 pm
content: Did you get it fixed?

author: USMC_Spike
author_rank: Regular Contributor
timestamp: November 15, 2017, 08:04:09 pm
content: I was waiting for a while now....Almost a two year long wait for the result fromscopeman?I'm too patient.Only a week long wait so far fromrafik.Gentlemen what have we found out? or nothing?

author: scopeman
author_rank: Frequent Contributor
timestamp: December 24, 2017, 01:53:29 am
content: I ended up replacing the module. Not my preferred method of repair but it now works and meets specs.SamW3OHM

author: UA3BL
author_rank: Newbie
timestamp: November 11, 2020, 10:23:10 pm
content: Quote from: scopeman on December 24, 2017, 01:53:29 amHello Sam, How did you do that? I face the same problem,73!

author: rafik
author_rank: Contributor
timestamp: December 19, 2020, 02:40:26 am
content: Greetings honorable gentlemen, I had really forgotten this post, the system does not notify if a response is received and also I do not dedicate to electronics full time so I forget to review my posts, please I present my apologies!The truth is that I solved how to get out of pulse mode. You have to press the AM button twice and then once the MOD ON / OFF button as soon as the RF generator has been turned on, the pulse mode text will immediately disappear from the screen. Solved !!I hope it helps someone.73!rafik