Technical opnion about wave generator with problem - Page 1
Forum section: electronics / testgear

author: israel
author_rank: Contributor
timestamp: August 08, 2013, 11:03:48 pm
content: Hi guys.I have this wave generator with some problems, are all under control except the display indication ... is deadI have seen that there is voltage in pin 3 of IC that varies as a function of the position of the frequency control. i suspect that the reason that the display does not show anything could be the IC HEF-4379VPthere a reliable way to know if the problem is that IC?I have found on the internet but is quite expensive. and before buying I would like to have some more expert opinion.attached images to see the team and the IC.sorry for my terrible englishBest regards

author: AlfBaz
author_rank: Super Contributor
timestamp: August 08, 2013, 11:29:47 pm
content: Have you checked for any output on the scan and data out pins?

author: tinhead
author_rank: Super Contributor
timestamp: August 08, 2013, 11:34:11 pm
content: the right trim pot didn't look good, check it first.

author: fpliuzzi
author_rank: Regular Contributor
timestamp: August 09, 2013, 12:25:17 am
content: Hello,The socket that the HEF-4379VP sits is in may be as tarnished as the right hand trim pot that tinhead pointed out. if you haven't done so already you may want to try lifting the chip up a bit on each side and then reseating the HEF-4379VP. The pins may be making poor contact. Worth a try anyway.Regards,Frank

author: israel
author_rank: Contributor
timestamp: August 10, 2013, 11:14:00 am
content: Quotewas one of the first things I thought.I researched a little more, and I think that might be the IC makes the voltmeter function to control the displayI thought at the decoder, but this was fine.Anyone know where I could get cheap HEF4739VP?The only site I found sells it at $ 62 + shippingRegards,

author: PA0PBZ
author_rank: Super Contributor
timestamp: August 10, 2013, 11:48:26 am
content: Are there any pulses on the scan lines (pins 10 - 13)?Is the thing oscillating (pin 25)?

author: israel
author_rank: Contributor
timestamp: August 10, 2013, 03:45:33 pm
content: QuoteThe tests show these results:1 --- 10.6820 v fixed2 --- GND3 --- The voltage varies according to the frequency and amplitude -4 mv to 1.8 volt4 --- 3.8993 v fixed5 --- no voltage6 --- 6.6758 v fixed7 --- no voltage8 --- 3.6862 v fixed9 --- no voltage10 -- 1.3440 v fixed11 -- 4.9380 v fixed12 -- 1.3462 v fixed13 -- 1.3460 fixed14 -- no voltage15 -- 5.114 v fixed16 -- 1.4945 v fixed17 -- 5.127 v fixed18 -- 3.3385 v fixed19 -- no voltage20 -- no voltage21 -- 4.9771 v fixed22 -- 4.9797 v fixed23 -- 3.5055 v fixed24 -- 4.9796 v fixed25 -- 3.2070 v fixed (no clock in scope)26 -- 3.3875 v fixed (not response at 250 khz)27 -- 4.9796 v fixed28 -- 4.9820 v fixedI see that pin 25 delivers no signal, according to the manual the clock signal is 250 KHz. I tried to inject a 250 KHz signal on pin number 26 (clock input) to see what happened, but there is no result.

author: PA0PBZ
author_rank: Super Contributor
timestamp: August 10, 2013, 03:58:38 pm
content: Well, if the thing is not oscillating and there is a supply voltage, it might be dead, I don't see anything like an enable line...All you can do is check the L, R and C on the clock pins, but if these are OK I think it's game over for the IC.I did a quick search and all I found is the one you found too for $62.