Tek 465 - Missing IC - Page 1
Forum section: electronics / repair

author: dan3460
author_rank: Frequent Contributor
timestamp: November 16, 2016, 12:16:24 pm
content: This is the 3rd scope that I got this week. It had sticker saying that did not have vertical or horizontal deflection. The dot on the screen did not respond to changes on volt/div or time/div, but it did respond to the position knobs. I had repaired a few of this before so I thought should not be difficult to repair. Undressed the scope, checked the voltages just a tad low.I started to trace back the horizontal deflection, from the pins that connect to the tube. Nothing, flat line. Move back a little, to a transistor. Nothing. Jump to another page of the manual, located other transistor in the path. Nothing. Decided to check the IC (U870) that controls the sweep and I have an empty socket.I carefully looked at the parts in the manual and yes this is a proprietary IC. Quick search on the web it can be had for $50, more than double of what I paid for the scope. And if they took the IC from here, probably to donate to another scope tells me that this scope must have other problems.Sorry for the long missive. Is there another solution instead of this IC? Is this scope just became parts scope? Ideas?

author: oldway
author_rank: Super Contributor
timestamp: November 16, 2016, 02:05:41 pm
content: If you use to repair analog oscilloscopes, you probably know that it's often necessary to have a faulty oscilloscope to retrieve parts.I just bought a Hameg 203-4 with a defective transformer, I paid 20 euros, it is worth to recover parts.Nothing but the cathode ray tube is worth more than the 20 euros I paid.

author: dan3460
author_rank: Frequent Contributor
timestamp: November 16, 2016, 02:17:04 pm
content: Indeed, it may be a good parts scope.In the other hand, it could be an interesting project to try to replicate the IC with some parts. There is some information available that tells the basic functionality of the chip.I know that this will be a lot more time and money that is worth it but this kind of thing really grab my attention.

author: David Hess
author_rank: Super Contributor
timestamp: November 16, 2016, 03:22:56 pm
content: The only replacement for U870 is another Tektronix 155-0049-xx (-00, -01, and -02 should all work as far as I know) custom integrated circuit however this sweep control IC was used in several products besides the 465 including the ubiquitous 7B50A, 7B53A, and 7B92A 7000 series timebases.

author: tggzzz
author_rank: Super Contributor
timestamp: November 16, 2016, 03:47:37 pm
content: Quote from: dan3460 on November 16, 2016, 12:16:24 pmFleabay shows item 272435914000 for ~$20. I have no experience of that particular Israeli supplier.

author: dan3460
author_rank: Frequent Contributor
timestamp: November 19, 2016, 07:11:53 pm
content: Solved the problem of the missing IC, I bought a 7B80 plug in from ebay for $25 including freight. Took the IC from there plug it in the 465 and I get something resembling a trace. It is not sweeping correctly but is basically working. I also was missing the horizontal position knob and I think that I can use the one for the plug in.I'll post in regards of the restoration of the scope.Thanks every one.

author: dan3460
author_rank: Frequent Contributor
timestamp: November 20, 2016, 01:22:50 am
content: First thing that I have to do is to replace the main power caps. I have ordered the caps that I didn't have so it will be a few days before I can come back to this scope.

author: David Hess
author_rank: Super Contributor
timestamp: November 20, 2016, 01:25:31 am
content: I did not think you would get a replacement so quickly. I should have recommended doing what tests you can to make sure an external fault did not damage the original sweep control integrated circuit.

author: dan3460
author_rank: Frequent Contributor
timestamp: November 20, 2016, 07:46:43 pm
content: Every thing seems to be working fine, I have just a little ghosting after the sweep but I thing that is because of the power supply. One of the big caps is not filtering at all and the others are not much better. I'll keep posting.