TOELLNET TOE7401 function generator repair. Need schematics / service manual ? - Page 1
Forum section: electronics / repair

author: Noy
author_rank: Frequent Contributor
timestamp: December 12, 2018, 10:52:35 pm
content: Hi guys,i have shot a TOE7401 on ebay.It looks like its partly working. The output works with a high impedance probe / 50 Ohm BNC cable to my DS1054z without a 50 Ohm throughput termination and it seems fine. But as soon as i connect it with a 50 Ohm throughput terminator the signal is "dead". I think the output amplifier is broken.Does somebody have a service manual or a schematic from the function generator?

author: coromonadalix
author_rank: Super Contributor
timestamp: December 13, 2018, 02:41:58 am
content: Well if you ask them directly ? or maybe tell them under an non diclosure agreement, maybe they could send you an service manualyou never knowthe only service manual ive found is this :https://elektrotanya.com/toellner_7740,7750_function_generator.pdf/download.htmlIt may help you in some way ? maybe some ressemblance in the output power stage, you should have an 20 volts output with an +/- 10 volts offset on a 50 ohms load ??

author: babysitter
author_rank: Frequent Contributor
timestamp: December 13, 2018, 12:14:43 pm
content: Toellner is nice, they give you the manuals, I got it in hours after my request(but was asked to keep it.)

author: ktulu
author_rank: Regular Contributor
timestamp: December 13, 2018, 08:14:18 pm
content: Just a few days ago I was also searching for TOE 7404 schematic, service manual.I sent 2 mails to Toellner, but received no reply.(the manual on that link posted by coromonadalix was uploaded after that)I have the newer model with frequency counter, and a completely different all smd PCB.There is a 6 page long pdf that I've found with a quick search, that should have 16 pages with schematic and calibration instructions, but unfortunately it is cropped.

author: Noy
author_rank: Frequent Contributor
timestamp: December 15, 2018, 09:06:06 pm
content: I asked Toellner already a few weeks ago.Got some manuals with everything in it but it was for the old fully THT variant. I have a newer full SMD one completly different mounting references. So it is not useable for me.But i found the issue, Oxidation at the output fuse. Cleaned it with a glass pencil.But i think i need to adjust it new.And for this i need a manual which is for my version to find the correct potentiometer in the pcb.

author: mldevw
author_rank: Contributor
timestamp: December 15, 2018, 09:15:38 pm
content: Hi,I was in the same situation as you a few days ago, but then I foundhttp://www.ko4bb.com/getsimple/index.php?id=download&file=06_Misc_Test_Equipment/Toellner_TOE_7402_7404_7702_7_LF_signal_generator_operating_and_Service_Manual.pdfIt's a great manual with detailed schematics.Good luck fixing your device!

author: Noy
author_rank: Frequent Contributor
timestamp: December 15, 2018, 09:37:33 pm
content: I have this manual already. But it is for THT variant.Please see my pictures. On the small Board we're 2 thyristors mounted. For example the potentiometer in this Board is completly missing in the old manual.Maybe i can find out which potentiometer is which with the old schematic with some deeper searching.

author: Noy
author_rank: Frequent Contributor
timestamp: December 15, 2018, 09:46:40 pm
content: Now with Pictures...

author: Noy
author_rank: Frequent Contributor
timestamp: April 11, 2019, 08:05:55 pm
content: Back working....Dirt / Oxid on the contacts from the fuse caused the problem...Cleaned it with a glaspencil and now everything is fine.