Wavetek 288 Fails selftest - Page 1
Forum section: electronics / repair

author: VE7HR
author_rank: Contributor
timestamp: January 24, 2022, 09:31:26 pm
content: I am hoping an expert will jumps in and point me to where how to troubleshoot the new to me Wavetek 288.It was working recently as the seller has posted working pictures of it here previouslyGot it home and powered it up and get the following error messages after 30 minutes then running the calibrate.ERR VCGZEROI have copy of manual but is does not tell me much.What are the normal failure modes and common things to check.ThanksDave

author: VE7HR
author_rank: Contributor
timestamp: January 24, 2022, 10:41:58 pm
content: Here is theerror.Dave

author: SilverSolder
author_rank: Super Contributor
timestamp: January 24, 2022, 11:06:32 pm
content: This manual is for a different model from the same era - it seems to have a Theory of Operation that mentions how VCGZERO is used in the system. Perhaps something can be gleaned from that.https://radionerds.com/images/a/a4/TM_11-6625-3198-40.PDF

author: wn1fju
author_rank: Frequent Contributor
timestamp: January 25, 2022, 12:56:23 pm
content: My unit did the same thing. What I did was to remove the battery on the motherboard, wait 10 minutes, reinstall the battery and then run through the complete calibration (which involves turning a few pots). My thought was that the calibration constants held in memory somehow got corrupted. It then threw a different error! I ran the AutoCalibrate several times in a row until all of the errors magically disappeared. Several people on the forums have commented over the years on how flaky the whole Calibrate/AutoCalibrate process seems to be.The manual on the SG-1288/G referenced in the post above has much better information than the Wavetek manual.

author: VE7HR
author_rank: Contributor
timestamp: January 25, 2022, 03:38:22 pm
content: Thanks for this information,I will read through the calibrations and give it a go.When I looked at the manual it did look very familiar in places.Thanks you very muchDave

author: VE7HR
author_rank: Contributor
timestamp: January 25, 2022, 09:21:12 pm
content: So I think I am going in a circle.Using the posted manual.I have done the reset and battery remove replace with the button A2SW1 and I get the ERR VCGZERO. When you run through the trouble shooting if you get the same error you are supposed to chase. Since there is not a specific VCGZERO seem to be gong in a loop nowhere.When you say complete calibration as you saying all 5 Adjustments in section 2-28?I suspect this will be last piece of wavetek I every touch.Dave

author: SilverSolder
author_rank: Super Contributor
timestamp: January 25, 2022, 10:02:14 pm
content: Is section 2-17 of any use?2-17. FUNCTION ERROR TEST.DESCRIPTIONThis test is used to isolate ERR error codesof COMP8+, COMP9+, POSVCGOFF, SCALE,SNEGVCGOFF, SPOSVCGOFF, SWP LENGTH, SYMM50PCT, TORFR3, TORFR4, TORFR5, TORFR6,TORFR7,VCGZERO, VFREQO, VFREQOS, and VTRIBAL in the Signal Generator (fig. FO-1) to the malfunctioning assembly [...]

author: VE7HR
author_rank: Contributor
timestamp: January 26, 2022, 12:03:28 am
content: W1FJU,And you expand on how you did the calibration. Let me know what sections to follow.It now powers up with Cal required Calibration off.So I have blown away calibrations.It is not clear to me which section to follow. Section 2-28 is marked Adjustments. Is this the process to follow?ThanksDave

author: wn1fju
author_rank: Frequent Contributor
timestamp: January 26, 2022, 02:16:21 am
content: If I recall (it has been several years), I used paragraphs 2-28 to 2-34 of the Army SG-1288/G manual. It may take a couple of tries, particularly if it throws an error during the adjustments. The manual makes a strange comment at the beginning of the adjustment section about never performing all the adjustments at the same time. I never understood that comment fully, but I interpreted it to mean at the start of each adjustment, you should run through the initialization routine (hold down the switch on the motherboard while pressing the front panel calibrate key).Even if you get it to go smoothly through these adjustments, when you later try the autocalibrate function from the front panel, it may throw an error. I just kept doing the autocalibrate until it eventually passed. It could be that the autocalibrate routines only allow a small change from what is stored in memory, and it takes a few tries to get enough excursion. But I'm only guessing.And if that isn't enough, I've had mine say that calibration is required on startup several months later for no apparent reason. As I said earlier, it all seems quite flaky to me and I wish I had concrete evidence of what is happening.Incidentally, in the times when it didn't pass calibration or told me that it needed to be calibrated on startup, the unit still seemed to perform quite accurately to the point where I couldn't easily see anything out of spec.

author: VE7HR
author_rank: Contributor
timestamp: January 26, 2022, 04:36:15 am
content: It would appear mine must have another fault as the output does not look good. Or to be more correct not there.I think it time to put this back on the shelf of broken dreamsThanks for everyone's help.Dave