HP8350B  sweep generator. Need the scan of figures 8-40, 8-43, 8-45 - Page 1
Forum section: electronics / repair

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: March 14, 2025, 03:22:43 pm
content: Dear All,I am trying to repair a HP8350B RF sweep generator. The 20V, 40V, 5V power supplies seems to be OK, but the 15V has problems ( both -15V and 15V).Too go further, I would like to have the schematics, but the one that are in the available user manual scans are not readable. I would appreciate if someone can send me a proper scan of the following figures, I would greatly appreciate.figure 8-40 A6/A7 block diagramsfigure 8-43 A6 rectifierfigure 8-45 A7 regulatorThanks

author: Tony_G
author_rank: Super Contributor
timestamp: March 14, 2025, 11:00:58 pm
content: ArtekManuals.com has the OM & SM available - You can get everything they have for ~US$10The scan quality is typically excellent especially on the schematics.TonyG

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: March 15, 2025, 04:15:42 pm
content: Thanks for the info Tony.meanwhile I got the 8350A schematics, so I think this will be OK, but a next time, I will look to Artek. I looked on their web site. Everything looks fine. It is just too bad that they dont provide any info on the scanned documents.

author: Tony_G
author_rank: Super Contributor
timestamp: March 15, 2025, 05:56:28 pm
content: NP - Glad to help.I have many scans from Artek that are all of great quality, so I can heartily recommend them as a source for manuals. (I've bought their scans even when I have the physical manual because the ability to search, etc, is worth it.) Good luck with the repair.TonyG

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: March 15, 2025, 08:55:41 pm
content: I have now made a lot of progress.I found that the two fuses of A6 were blown (see pic). I also reformed all the big caps of the power supply that seem OK.recalibrate all voltagesproceed also to some of the other calibration.The good news is that now I have a functioning unit (with 83525A plug-in)but I have an offset of 13.6 Mhz in the frequency. If I ask 113.6 Mhz, I get 100Mhz.Does anybody knows how to fix that ?

author: coppercone2
author_rank: Super Contributor
timestamp: March 15, 2025, 09:14:31 pm
content: I will say a prayer for you, to get my 8350 to work I had to combine two into one, and buy cards on top of it, and totally re-skin the mother board.I got stress seeing the number 8350 in the thread titleseriously fuck that thing, I spent all that effort fixing this magic broom, I still don't know how to fly on it. If life was fair you should be able to strap a chair to this thing and fly around the universe

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: March 15, 2025, 09:45:07 pm
content: Thanks Coppercone, this will surely help !My unit seem to be in quite good shape, although I got it in the trash, but I must say I dont understand everything.There is a quite complex procedure for the "Frequency Control Adjustments" (p. 5-34, 5-35). I have followed everything, and get all voltages right at the accuracy of my multimeter (sometimes I am missing one digit).But as I say, at the end I have this 13.6 Mhz offset in the frequency

author: coppercone2
author_rank: Super Contributor
timestamp: March 15, 2025, 09:48:23 pm
content: Did you check for massive corrosion damage from the battery pack.Get rid of that thing ASAP. The wires wick electrolyte and it will even go into the DSUB37 or whatever connector there is on the back and grow crystals in there. It will also get into the PCB coating.You seriously might have corrosion damage with that bullshit 'Alien 3' battery pack

author: coppercone2
author_rank: Super Contributor
timestamp: March 15, 2025, 09:54:07 pm
content: But 13.6 sounds like a suspicious number. Isent that related to some kind of IF shift or something on some older equipment to look for fake signals... just racking my brain hereI seem to assosiate that number with a spectrum analyzer, but it could be 12.7one of them had a button that would shift something by around 10MHz to let you determine which signals are image products or whatever

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: March 15, 2025, 10:12:01 pm
content: The battery pack was not totally dead ( 3V) and was leaking, but just a little. I had no damage from it.Of course I removed it.I dont understand yet the use of it.All the tests I made were in the CW mode. I would like to have a good RF source and with its 10 Mhz to 8.4 Ghz, plug in, this is perfect for me.I just have now to solve this frequency offset issue. I measure the frequency with my scope. Unfortunately, my best scope ( a TDS3032 ) had just chosen this time to be very silly and is asking for disquettes to upgrade the firmware. I will have to fix that too. meanwhile, I used a TDS 220 that did the job up to 300 Mhz (with a decrease of amplitude of course). I may try with other scopes I have.In fact, I just got the HP8350B yesterday, so I am already quite happy with the result.Here are some additional pics. Lots of gold in this unit (probably of 1987).

author: coppercone2
author_rank: Super Contributor
timestamp: March 15, 2025, 10:16:42 pm
content: Ok so the 113MHz is coming out of the module you plugged in right. (output is 10MHz to 8GHz, you set for 100MHz)That connector in the back that controls it,So you determined that every signal and power rail in the back panel connector going to the sweeper module is correct, right? Because the 8350B is just adjustments for the plugin you use..I forgot HOW its controlled, but you should be able to determine every setting that the module is configured with by checking the back panel connector.I think some people just figure out how to use the module with a minimum control system without the 8350b mainframe ?Maybe I missed it, but I don't think you determined if its the 8350B mainframe or the plugin module that is malfunctioning?

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: March 15, 2025, 10:21:52 pm
content: Quote from: coppercone2 on March 15, 2025, 10:16:42 pmWhen I set 113.6 Mhz on the keyboard, I get 100Mhz.When I set 213.6 Mhz on the keyboard, I get 200 MhzI will have to do that more in a systematic way.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: March 15, 2025, 10:25:24 pm
content: Quote from: coppercone2 on March 15, 2025, 10:16:42 pmWhich connector ? In the 8350B, or in the Plug-in (835225A) ?

author: coppercone2
author_rank: Super Contributor
timestamp: March 15, 2025, 11:56:02 pm
content: the 8350 b controls the plug in which does all the RF stuff.We don't know if its the plugin or 8350byou need to check the connector betwen the plugin and 8350 b to see if the settings are nominalif so, its the module, if not then it could be the mainframe or the module (i.e. its being loaded)the connector is a complex arrangement of different control settings, you need to set it, figure out what they should be, and see what they arethere is a common 'protocol' of signals to the different modules, since there is about 20 modules that can be controlled by the 8350. so the different signals on the connector are well definedfor instance, lets say something uses a 0-5v control. there could be a offset drift or scaling error or something on that signal chain which leads to a setpoint error. or some RF module in the plugin can be damaged, and not create the correct signal when prompted to

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: March 18, 2025, 09:04:01 am
content: I have made all the calibration sequences on the HP8350B, and everything is fine.I have just this 13.6 Mhz offset, but this is easily taken care by the OFFSET VERNIER feature.I have checked that this is really an offset, and once the VERNIER OFFSET is set to 13.6Mhz, everything is perfect.So I am now consider that my 8350B is fully functional and restored its normal operation. Will put it in good place in my workbench.Thanks Coppercone for the feedback.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: March 18, 2025, 02:17:39 pm
content: some final pics showing that the units works well

author: coppercone2
author_rank: Super Contributor
timestamp: March 18, 2025, 10:39:35 pm
content: So it looks like maybe it was offset drift from some thing in the signal chain and it was still within spec of the trimmer.glad it works

author: Tony_G
author_rank: Super Contributor
timestamp: March 18, 2025, 11:41:57 pm
content: My $0.02,I'm not remotely an 8350B expert but I don't think the front panel offset vernier is meant to tune a frequency discrepancy back to a "true" value.There has to be a systemic reason for the value being constant regardless of what is specified as the frequency.Now that said, if it works and you're fine with it then there is no need to break into jail by trying to fix it.TonyG

author: coppercone2
author_rank: Super Contributor
timestamp: March 18, 2025, 11:47:04 pm
content: I don't know what it does. Does it program a oscillator digitally to tune it?These things are NOT known for their frequency stability btw. Thats why nicer equipment has TXCO boxes on it . I think the goal of this instrument is to sweep a veery broad band range.13 MHz seems like alot though (10% error). I think the main decision has to be taken to repair it depending on if1) the offset holds across the range to a reasonable accuracy2) the drift over time is within specbut being practical, for broad band VNA sweep, it hardly matters. The things you test on a VNA are like stable in comparison to everything else, since its basically wave guide or LC circuits, you won't be tracking oscillator drift or something with this. Not sure how high of a Q the things you plug into this will be.You do need to make sure its stable though, if you are doing something like adjusting a complex array of tuning screws, if it starts moving around on you then its b ad