Author Topic: [SOLVED] HP 6227B dual DC power supply - oscillation in master channel  (Read 10040 times)

0 Members and 1 Guest are viewing this topic.

Offline bitseeker

  • Super Contributor
  • ***
  • Posts: 9057
  • Country: us
  • Lots of engineer-tweakable parts inside!
Re: [SOLVED] HP 6227B dual DC power supply - oscillation in master channel
« Reply #25 on: March 29, 2019, 05:41:33 pm »
That's some really clean output. What an excellent outcome.

It's interesting that the 180µF caps reflect the usual capacitor miniaturization, but the 4000µF ones don't. The latter seem to be the same size as the original.

New axial caps look so much better in those axial locations. I'm glad you got them rather than "converting" to radials.
TEA is the way. | TEA Time channel
 

Offline kj7e

  • Frequent Contributor
  • **
  • Posts: 911
  • Country: us
  • Damon Stewart
Re: [SOLVED] HP 6227B dual DC power supply - oscillation in master channel
« Reply #26 on: March 29, 2019, 07:26:18 pm »
The hard part was to find caps BIG enough not to look goofy, so the higher working voltage parts increased the size some.

The supply works great, but gives off a considerable amount of heat from the capacitor bleed resistors. I'm considering changing out the 1k 5w resistors for 5k 5w.  I know this will effect some aspects of the specifications but I'm not a government lab.
« Last Edit: March 29, 2019, 08:39:30 pm by kj7e »
 
The following users thanked this post: Sparky

Offline bitseeker

  • Super Contributor
  • ***
  • Posts: 9057
  • Country: us
  • Lots of engineer-tweakable parts inside!
Re: [SOLVED] HP 6227B dual DC power supply - oscillation in master channel
« Reply #27 on: March 29, 2019, 08:27:15 pm »
That sounds like a pragmatic solution. It's a new century. Don't waste power like it's 1999. ;D
TEA is the way. | TEA Time channel
 

Offline Tomorokoshi

  • Super Contributor
  • ***
  • Posts: 1212
  • Country: us
Re: [SOLVED] HP 6227B dual DC power supply - oscillation in master channel
« Reply #28 on: March 29, 2019, 08:34:20 pm »
...

I'm considering changing out the 1k 5w resistors for 5k 5w.  I know this will affect some aspects of the specifications but I'm not a government lab.

I replaced mine with either 5k or 10k. The only effect I see is when it's turned off, the needle does a little bounce on the way down.
 
The following users thanked this post: Sparky, kj7e

Offline SparkyTopic starter

  • Frequent Contributor
  • **
  • Posts: 449
  • Country: us
Re: [SOLVED] HP 6227B dual DC power supply - oscillation in master channel
« Reply #29 on: March 31, 2019, 01:19:53 am »
Mine starts with serial # 2451A, all the caps have date codes from 1984, but I suspect it was made a bit later than that due to the rocker style power switch, however mine still has the course and fine pots, not the 10 turn pots the OP's has.  Sparky, what is your serial number?

Thanks for the detailed notes and repair report, kj7e!  (Sorry for the late reply -- I've been on travel away from my lab!)  I enjoyed to read about your progress, and the links to the replacement parts is great help for future!  I don't have a LCR meter so I can't measure the large capacitors --- I think might be time to get one!  ;D

The serial number on my unit is: 3314A-xxxxx

Great contribution to this thread!  :-+
 

Offline kj7e

  • Frequent Contributor
  • **
  • Posts: 911
  • Country: us
  • Damon Stewart
Re: [SOLVED] HP 6227B dual DC power supply - oscillation in master channel
« Reply #30 on: March 31, 2019, 03:38:38 am »
Mine starts with serial # 2451A, all the caps have date codes from 1984, but I suspect it was made a bit later than that due to the rocker style power switch, however mine still has the course and fine pots, not the 10 turn pots the OP's has.  Sparky, what is your serial number?

Thanks for the detailed notes and repair report, kj7e!  (Sorry for the late reply -- I've been on travel away from my lab!)  I enjoyed to read about your progress, and the links to the replacement parts is great help for future!  I don't have a LCR meter so I can't measure the large capacitors --- I think might be time to get one!  ;D

The serial number on my unit is: 3314A-xxxxx

Great contribution to this thread!  :-+

Wow, yours is a very late model, after 1993.  Reading the manual, any year could have been ordered with the 10t pots.  I would suspect the rest of your caps are in good shape.
 
The following users thanked this post: Sparky

Offline bitseeker

  • Super Contributor
  • ***
  • Posts: 9057
  • Country: us
  • Lots of engineer-tweakable parts inside!
Re: [SOLVED] HP 6227B dual DC power supply - oscillation in master channel
« Reply #31 on: March 31, 2019, 03:44:05 am »
Wow, Sparky's is quite new. Although both your and Sparky's supplies have rocker switches, the badges and knob style also reflect the age difference.
TEA is the way. | TEA Time channel
 
The following users thanked this post: Sparky, kj7e

Offline SparkyTopic starter

  • Frequent Contributor
  • **
  • Posts: 449
  • Country: us
Re: [SOLVED] HP 6227B dual DC power supply - oscillation in master channel
« Reply #32 on: March 31, 2019, 06:46:56 am »
Wow, yours is a very late model, after 1993.  Reading the manual, any year could have been ordered with the 10t pots.  I would suspect the rest of your caps are in good shape.

Oh, I did not know that!  How does one determine the date from the serial number?

And yes, I think you're right with the 10-turn pots -- I had same understanding from the manual that it was an option at time of order.  I'm not sure if HP decided to switch to 10-turn pots by default after sometime though.
 

Offline SparkyTopic starter

  • Frequent Contributor
  • **
  • Posts: 449
  • Country: us
Re: [SOLVED] HP 6227B dual DC power supply - oscillation in master channel
« Reply #33 on: March 31, 2019, 06:48:58 am »
Wow, Sparky's is quite new. Although both your and Sparky's supplies have rocker switches, the badges and knob style also reflect the age difference.

I got lucky with my unit on eBay!  I did not know it was a newer or older one!

I don't mind the classic Black + Blue "hp" badge :D
 

Offline bitseeker

  • Super Contributor
  • ***
  • Posts: 9057
  • Country: us
  • Lots of engineer-tweakable parts inside!
Re: [SOLVED] HP 6227B dual DC power supply - oscillation in master channel
« Reply #34 on: March 31, 2019, 04:15:13 pm »
The first two digits of the serial number, plus 60, is the year of the design that the unit is based on. It's not the year of manufacture, but will give you an idea of the oldest it could be. Date codes on components will then be able to give you a more accurate estimate of its year of manufacture.
TEA is the way. | TEA Time channel
 
The following users thanked this post: Sparky

Offline SparkyTopic starter

  • Frequent Contributor
  • **
  • Posts: 449
  • Country: us
Re: [SOLVED] HP 6227B dual DC power supply - oscillation in master channel
« Reply #35 on: April 01, 2019, 06:55:23 am »
The first two digits of the serial number, plus 60, is the year of the design that the unit is based on. It's not the year of manufacture, but will give you an idea of the oldest it could be. Date codes on components will then be able to give you a more accurate estimate of its year of manufacture.

Thanks!  That's good to know!  Next time I open it up I will look for date codes on few main components!  :-/O
 

Offline kj7e

  • Frequent Contributor
  • **
  • Posts: 911
  • Country: us
  • Damon Stewart
Re: [SOLVED] HP 6227B dual DC power supply - oscillation in master channel
« Reply #36 on: April 04, 2019, 06:17:36 pm »
I changed out the 1K 5w bleeder resistors R76(A), R77(A) for 2.5K 5w parts.  Much better, rather than 2.5w of heat each, now down to 1w each.  They still get warm but you can put your finger on them now, before they would burn you.  Going to play with the VR3 bias resistors R75(A) some.  I have a feeling there is ample head room here and the bias current can be cut down some.

2.5K 5w resistors used;
https://www.digikey.com/product-detail/en/vishay-dale/ALSR052K500FE12/ALSR5F-2.5K-ND/257352



 
The following users thanked this post: Sparky, bitseeker

Offline bitseeker

  • Super Contributor
  • ***
  • Posts: 9057
  • Country: us
  • Lots of engineer-tweakable parts inside!
Re: [SOLVED] HP 6227B dual DC power supply - oscillation in master channel
« Reply #37 on: April 05, 2019, 02:37:47 am »
Cool. I still can't quite get over the size of those caps. ;D
TEA is the way. | TEA Time channel
 

Offline kj7e

  • Frequent Contributor
  • **
  • Posts: 911
  • Country: us
  • Damon Stewart
Re: [SOLVED] HP 6227B dual DC power supply - oscillation in master channel
« Reply #38 on: April 07, 2019, 01:06:47 am »
Okay, found almost no change in VR3 (4.32v 1w zener) when changing the bias current limit resistors R75(A).  Stock 135 Ohm, 18v drop, ~133mA bias current, 2.4 watts gets the resistors very hot and the zener gets warm with almost 0.6w to dissipate.  Replaced them with 250 Ohm 5 watt, now 72mA bias current for 1.3 watts of dissipation, zener is a bit cooler dissipating 0.3 watts.  No problem with regulation, the zener voltage did drop from 4.25 to 4.18v.  The amount of heat out of the top of the supply is much improved.  I feel very comfortable leave this supply on all the time now.

« Last Edit: April 07, 2019, 02:51:57 am by kj7e »
 
The following users thanked this post: Sparky, bitseeker

Offline bitseeker

  • Super Contributor
  • ***
  • Posts: 9057
  • Country: us
  • Lots of engineer-tweakable parts inside!
Re: [SOLVED] HP 6227B dual DC power supply - oscillation in master channel
« Reply #39 on: April 07, 2019, 04:02:57 am »
That's an excellent result. Thanks for documenting it (for when I get one of these :)).
TEA is the way. | TEA Time channel
 
The following users thanked this post: Sparky

Offline SparkyTopic starter

  • Frequent Contributor
  • **
  • Posts: 449
  • Country: us
Re: [SOLVED] HP 6227B dual DC power supply - oscillation in master channel
« Reply #40 on: April 07, 2019, 05:13:34 am »
Okay, found almost no change in VR3 (4.32v 1w zener) when changing the bias current limit resistors R75(A).  Stock 135 Ohm, 18v drop, ~133mA bias current, 2.4 watts gets the resistors very hot and the zener gets warm with almost 0.6w to dissipate.  Replaced them with 250 Ohm 5 watt, now 72mA bias current for 1.3 watts of dissipation, zener is a bit cooler dissipating 0.3 watts.  No problem with regulation, the zener voltage did drop from 4.25 to 4.18v.  The amount of heat out of the top of the supply is much improved.  I feel very comfortable leave this supply on all the time now.

Great update!  Thanks for this info!  I've been concerned about the heat...but I didn't look into what is required to reduce the heat output.  This is a great mod and I will definitely keep this in mind.  Not a bad idea at all to have it run a little cooler :)


That's an excellent result. Thanks for documenting it (for when I get one of these :)).
Ahhh yes, when not if;)  Am looking forward to your write up!  :D
 

Offline Jamieson

  • Contributor
  • Posts: 30
  • Country: us
Re: [SOLVED] HP 6227B dual DC power supply - oscillation in master channel
« Reply #41 on: April 28, 2019, 02:46:48 am »
Thanks for documenting your experiences with the caps in this supply. I recently picked one up, serno 1607A, so ~1976. Works like a champ clean and quiet, a real gem of a supply. I love that the HP manual has full schematics and several pages describing in detail how each sub-circuit works. It's like a little textbook on PS design. Ah, vintage HP -- by engineers for engineers, marketing be damned!

 
The following users thanked this post: Sparky

Offline Tabloka

  • Contributor
  • Posts: 17
  • Country: de
Re: HP 6227B dual DC power supply - oscillation in master channel
« Reply #42 on: September 07, 2023, 02:08:00 pm »
@Tomorokoshi, duak: I have completed tests of the reference and bias voltages, and also checking the the output bypass capacitor and a few others mentioned in the manual.  Results are as follows:

2) I performed the reference and bias voltage measurements as indicated in the operators manual (see attachments). 


Hello Sparky,

I know that this thread is a very old one but now I have trouble with my HP 6227B and this thread helps me a little bit to understand the supply. My supply worked fine for many years until the meter of the slave channel jumped to over 30 volts and then went dead. I checked the F2 fuse and find it blown. Okay maybe an easy repair. I changed the fuse against a new one and since then the slave channel is not adjustable and the meter of the slave channel says over 30 volts and the measured output is 47,5 volts at the front connectors.

Like the manual at 5-62 d. 'I isolated the crowbar from supply by disconnecting anode of CR4' to measure the reference and bias voltages. Step 2 to 6 is no problem and the numbers are quit good but step 1 I get odd numbers. For the master I read 6.0 volts and for the slave -16.7 volts. Both should be +27.5 volts.

Do I have the wrong TPs? For TP32 I put the common lead to the anode of VR2 and for TP12 I put the positive on the plus of the C6 cap.

BTW the master is still working fine. It is adjustable and with the voltage control turned fully clockwise I get 25.0 volts on the meter and also measured.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf