HP 6209B DC Supply - Page 1
Forum section: electronics / repair

author: orion242
author_rank: Unknown
timestamp: July 02, 2015, 01:54:13 am
content: So I picked one of these up recently and its needs some TLC.Symptom - No regulation, outputs ~530vdc regardless of controls.http://www.keysight.com/en/pd-1000001527%3Aepsg%3Apro-pn-6209B/single-output-power-supply-0-320-vdc?&cc=US&lc=engTroubleshooting.Checked all the voltage rails, all fine more or less where they should be. Checked test points 31, 33, 37, 38, 41, and the +16v rail. All good.Checked voltages in table 5-2, again all good.Check ESR/capacitance on all the large electros, no problems.Looked over the theory of operation and checked the SCR control block, had the signals on test points 68, 67, 66. All looked more or less fine.The "turn on control" seemed to be working. Upon power up the output is 0v for a few fractions of a second and then shoots to the moon, ~530v.In the process of checking voltages...I could smell some "hot". With the voltages at hand, was not too keen to be touching things, but it seemed R49 (center of the schematic near the main rectification bridge) was the source. R81 & R54 are also in contact with R49, so it could have been them. This makes sense since C14 had 530v across it when powered.Then as the manual recommends, I pulled CR35 and connected a DC supply across C14. Powered it back up and supplied C14 with 20vdc, output was 18.5v with no regulation. Output was ~1.5v minus whatever I fed in C14.Followed Table 5-4 and shorted Q4 E-B, no change in the output. Still 1.5v less than what I fed in. Checked Q6 out of circuit, passed diode checks no shorts. VR3, same no shorts passes diode check.I did a quick diode check on all the silicon between the output and CR35, and didn't find any issues. CR35 tested ok out of circuit, but since the turn on control works...I would thing at least CR35 or Q6 has to be working.Then I looked around the feedback path and found R12 (center of the schematic by the A7 terminal) & R1 (center of the schematic in the constant voltage comparator) open and R13 measures 151k out of circuit and should be 36K (org, blu, org, gold). R10, the voltage set pot, also not so linear any more. Still within 1-100K buts in has some bad spots. Looks like someone kicked in the shaft, its a bit dicky as Dave would say...So I have replacements coming for R12, R1, R13, & R10, the only issue I had was finding good replacements for R1 & R12. Digikey and mouser didn't carry any 2k 3W 5% 20ppm resistors available in small quantities, only 30ppm. Checked for 3-10W, still the same 20ppm seems impossible to find in small qty. Ordered the 30ppm anyway as I want to see if this guy comes to life. I assume this is not going to make a huge difference in the operation of the unit, but would prefer if I could stick with the original specs.Anyone know where I can find a source for small quantities of suitable replacements or is it pointless?Anything else that may be damaged from what I what I found so far?

author: Stray Electron
author_rank: Super Contributor
timestamp: July 04, 2015, 02:52:48 pm
content: Can you get 1 W 20ppm resistors and parallel them to get 3W? Or some kind of series-parallel combination to get the right resistance and wattage but it would need to be made of 20 ppm resistors.

author: orion242
author_rank: Unknown
timestamp: July 04, 2015, 08:08:46 pm
content: Ahhh, its the power rating + 20ppm that is making it impossible to find.Thanks for the tip.I'll add it to my next order. Got the 2k 30ppms and 100k pot yesterday. Put a 30K 1W in for R13 and decided to see if it came alive. No dice, still no regulation and it fried my new $15 100K pot. ARGH!Going back to the manual recommendations of checking Q6 & VR3 for shorts, I figured out VR3 was installed back to front. Previously I just did a quick short check in circuit on VR34. No wonder I didn't find shorts on a quick diode test, the damn thing was in backwards!I hooked Gary's resistor substitution board in for R10, installed VR3 correctly and tried testing it again with an external power supply. That was it, now at least the voltage regulation works. Put everything back on its internal power supply and voltage regulation is fixed. Quick check with 1ohm 100w resistor on the output and the current limiting seems to be good also. Fixed the burnt out power indicator with a led and everything but a new voltage adjust pot is good to go.Someone must have been dinking with it at some point and swapped around VR3.So another few day wait for more parts begins, but it looks like this guy is back in working order.Time to move on the the HP 6824A which is the next piece of sick gear in line.

author: orion242
author_rank: Unknown
timestamp: July 22, 2015, 01:13:55 am
content: Some pictures of this beast after fixing it, adding front output terminals, and a quick cal of the meter.Not a bad unit for the $10-20 I have into it.

author: AMR Labs
author_rank: Frequent Contributor
timestamp: March 27, 2025, 07:02:27 pm
content: Old thread but hoping someone might have the HP6209B service manual PDF that includes the PCB and component layout? I've got the one that seems to be available for download everywhere, its PN 06209-90003 from June 1969, and it has the full schematic but no board or component views. It is also meant for serial numbers starting with 7F1117 and above. Mine is SN 7F10xx so slightly bellow that breakpoint.The link to Keysight provided by the OP does not seem to work anymore, but would not be surprised that it was to the same version manual as the one I already have.Mine seems to be working fine, output voltage range checks out, and voltmeter scales are reading fine now after calibration (they where about 5V high).Only issues are some rather unusually stiff and somewhat hard to turn (but working) current 10-turn pot, and also when I switch the meter to 12mA range the needle pegs all the way to the left beyond zero, even without any load connected. The 120mA range seems ok other than it was reading a bit low, but calibration solved that. If I put a 10mA load and select the 12mA range it reads around 8mA, even after the previous calibration of the 120mA range, and pegs again to the left after a second or so once the load is removed. Guessing an out of tolerance resistor in the current meter circuit, but it would be easier and more convenient to track it down if I had the parts location on the main board as some parts label designations are obscured by the part itself. Otherwise guess I'll just map out all the board components.TIA.

author: TimFox
author_rank: Super Contributor
timestamp: March 27, 2025, 07:31:45 pm
content: A bit about my experience with the 6209B.I have two, both eBay purchases, which worked fine upon arrival.However, I tested the second one immediately with a power resistor load and hand-held DVM, with good results but when I connected it to a grounded load, it failed.I found that one of the rubber grommets that isolated the PCB from the chassis rail actually contacted a trace on the PCB: over time, it had charred the grommet (into charcoal) and presented a mediocre resistance to the chassis.I replaced that grommet with a plastic washer to fix that problem.I recommend checking that grommet, which I remember being located at the corner of the PCB closest to the left edge of the front panel (viewed from outside).

author: AMR Labs
author_rank: Frequent Contributor
timestamp: March 27, 2025, 08:24:22 pm
content: Noted, and again thanks for the heads up.

author: factory
author_rank: Super Contributor
timestamp: March 27, 2025, 10:13:28 pm
content: Quote from: AMR Labs on March 27, 2025, 07:02:27 pmI doubt the manual had a board component layout, the Harrison/HP PSU manuals are no where near as good as other HP manuals.The Agilent scan has updating (to 1989) & backdating (appendix A) change pages, the latter covers your unit.David

author: AMR Labs
author_rank: Frequent Contributor
timestamp: March 28, 2025, 11:30:16 am
content: I've also got a manual for the HP6207B which seems to be almost identical to the 6209B, and it does include the PCB parts location on the page just next to the full schematic. But it is very low-res and dark so very low contrast and not very usable other than to mostly locate the bigger components. Was hoping there might still be one 09B PDF manual out there that would have a clearer scan of that page. I do have the same manual that you posted the link for.Incidentally I was initially actually looking for a HP6207B instead of the 6209B as I did not need voltages beyond 160V, and would rather have 200mA. But there where none on ebay that where usable or even less at a sensible price. Then this 09B recently came up for $59.00 and I grabbed it. The only major difference between the 07B and 09B seems to be the former uses a two diode full wave main rectifier scheme, whereas the other uses a full 4-diode rectifier, hence the 160V against the 320V difference. Other components seem to be 99% identical, other than a couple of resistors around the driver and mixer amps, and of course the meter scale. I have not compared the transistors and diodes, but suspect they will also be identical. It may be feasible to convert mine to a 07B, but will see what I will do after fist fixing the 12mA scale meter reading issue.Might also try for a 09B paper manual on ebay, but so far did not find one there either, just one 07B. Will also ask at the HP IO group if someone could take a clear picture of just the PCB layout.

author: AMR Labs
author_rank: Frequent Contributor
timestamp: April 01, 2025, 06:08:33 pm
content: Turns out that C12 was bad. Its a 450uF 85V cap in the bias supply, and it only measured 135nF. The +43V supply was showing 34.2V, but when I set the DMM to AC there where 14VAC of ripple across the cap.After replacing the cap with 470uF 100V the voltage rail came up to +43.4V and the meter on 12mA scale no longer was pegging to the left, but now rather showing 4mA with no load. Had to adjust R38 and that brought it down to zero without affecting the general zero adjustment of the meter. Then went through the meter calibration routines for both voltage and current and all is good now.The other big caps, C14 and C20 both tested good so left them alone. Ripple at the output set to 320V with a 100mA load is about 1mV.