HP 6236B Triple Output Power Supply (w/ talk about GPD-3303S)

[JenniferG]

While I was on the forums all day here reading and posting messages, this poor lil' guy was chilly outside on the front porch!   Just opened up the box just now.  Wow it's really good condition.  Turned it on, the needle popped up to 20V, adjusted the voltage down and the needle went down.  The orange power light came on to the right of the power switch.  Well that's about all I've done with it.

Scored it for $45 plus $15 shipping from ebay -- a University that was selling it.  I feel like I got a bargain   Will be great for building & testing op-amps, sound modules etc.  It was recommended to me by a friendly Muffwiggler DIY guy who uses it.

Two channels / bipolar 0-20V, with current limiter set to 500ma internally.  And another channel of 0-6V if I recall at 2a.

I might be able to mod it, adding a dial to the front, allowing me to limit the current to a range of smaller values vs. a fixed 500ma.  But perhaps not necessary.  I'm not really sure as I'm a newb.

[bitseeker]

Yep, that's a good power supply. Although it doesn't have adjustable current limiting, it does have short circuit protection. Plus, it's got a big heatsink, so no noisy fan. It should serve you well.

Note that the supply's limits are printed on the front panel beneath the model and name.

[JenniferG]

I suppose I should get one of those GPD-3303S Linear DC Power supplies as well.  3 Channels, linear and up to 3A  0-30v.

Good for larger stuff.  I presume it has great adjustable current limiting as well.

To get through ARt of Electronics do I need one of these GPD-3303S or can I get by with the HP 20v 500ma HP I just got?

EDIT: Had I known about this Instek GPD-3303S deal I probably would of just bought it instead of this HP.  But I guess having two power supplies is good at times for certain things.  Been watching some vids on the GPD-3303S and wow it looks pretty darn terrific.  I can get one in almost flawless condition for $150 including shipping off ebay.  That along with the GDM multimeter for $100.. I'd be pretty set.

[bitseeker]

You should be able to get through AoE with the HP. One of the recommended power supplies is the HP E3630A, which is like your 6236B, but with digital displays instead of analog.

If you get one of the GPD-3303S, beware that there are two versions, but with the same model designation. One has all the banana jacks equally spaced and the other doesn't (channel 3 is spaced further from the other two). You don't want the one with the equally-spaced jacks because it has a voltage overshoot problem on Channel 3. There are a couple of threads here about it.

Some sellers don't know that there's a difference and have been known to substitute one for the other despite what the listing photos show. So, be sure to ask exactly what the one you're buying looks like. Of course, if it doesn't match the listing photos or description, you can return it under eBay's Buyer Protection policy.

[JenniferG]

You should be able to get through AoE with the HP. One of the recommended power supplies is the HP E3630A, which is like your 6236B, but with digital displays instead of analog.

If you get one of the GPD-3303S, beware that there are two versions, but with the same model designation. One has all the banana jacks equally spaced and the other doesn't (channel 3 is spaced further from the other two). You don't want the one with the equally-spaced jacks because it has a voltage overshoot problem on Channel 3. There are a couple of threads here about it.

Some sellers don't know that there's a difference and have been known to substitute one for the other despite what the listing photos show. So, be sure to ask exactly what the one you're buying looks like. Of course, if it doesn't match the listing photos or description, you can return it under eBay's Buyer Protection policy.

Thank you.  Just the info I was looking for with respect to which version of the GPD-3303S I should buy.

[mtdoc]

I have an HP 6236  (among other PSUs  ). It was one of my first power supplies.

I like it a lot.  The tracking outputs are nice when you are playing with op-amp circuits.  In some ways a lack of current limiting can be good when starting out since a lot of learning takes place when the magic smoke escapes...

You definitely scored well with that price and are well on your way to TEA membership.

But I guess having two power supplies is good at times for certain things. 

Ah em...  Yes -  two, three, ten, twenty.... some of us feel you can never have too many -- Speaking of which I just bought a GPD-3303S and need to send it back tomorrow due to the mix up on versions (seller did not send the one in the picture) that bitseeker is refering to.

[JenniferG]

So this basically: )

[bitseeker]

But I guess having two power supplies is good at times for certain things. 

Ah em...  Yes -  two, three, ten, twenty.... some of us feel you can never have too many

Yep, even when we do. This ITT liquidation is really hard on my TEA. But I've not succumb, yet.

[bitseeker]

So this basically: )

Yes!

[mtdoc]

Yep. I bought from a listing with the correct (bottom) picture but was sent one like the top picture.

Just to be clear, the overshoot issue is only on the fixed 2.5-3-5 V output on the far right. The 2 main outputs are fine. It's not really that big of a deal (and likely an easy fix) - but still - I purposely ordered one I thought would not have that issue.

So, I would recommend messaging any seller you buy from to be sure they know specifically what you want.

[JenniferG]

But I guess having two power supplies is good at times for certain things. 

Ah em...  Yes -  two, three, ten, twenty.... some of us feel you can never have too many

Yep, even when we do. This ITT liquidation is really hard on my TEA. But I've not succumb, yet.

Fortunately for me, since I am such an early user, I have excuses since I don't really have any gear :>

[JenniferG]

Going through the manual and it wants me to do a "TURN-ON CHECKOUT PROCEDURE". 

Been going through it.  But I skipped the steps where it wants me to short common to +6VDC and common to +20VDC, observing the amp meter.   LOL, I am afraid to! Bzzt!  Hopefully the current limiting works and I don't get sparks!

[Berni]

Going through the manual and it wants me to do a "TURN-ON CHECKOUT PROCEDURE". 

Been going through it.  But I skipped the steps where it wants me to short common to +6VDC and common to +20VDC, observing the amp meter.   LOL, I am afraid to! Bzzt!  Hopefully the current limiting works and I don't get sparks!

Well better that you know the current limiting works rather than having everything blow up when you connect your circuit to it, including your circuit you worked hard on.

Besides if the PSU does blow up if you do that then you can go and fix it so it works like it should and you will learn a lot while troubleshooting and repairing it. The old HP gear is easy to fix due to having nice service manuals and it brings a lot of satisfaction when you do manage to get a old quality piece of gear working like new again.

By the way don't worry too much about it, even crappy non current limited power supplies tend to survive a short circuit for a second or two since the failures tend to be purely thermal and it takes a while for things to heat up. So if current limiting doesn't work it should just output way too much current rather than suddenly blow up with sparks and smoke.

[JenniferG]

Thanks. I did the the current limiting tests and the ammeter showed the correct current values, according to the instruction manual.

Someone on muffwiggler just shared this mod he did to his 6236B -- smd led lights above the meters.  I so want to do this!  I was thinking about lighting up the meter last night, even before I saw this photo.  Makes it so much easier to read!

[bitseeker]

That meter lighting mod looks good. I've been considering doing that to some of my supplies, but with amber LEDs to give a warm glow like the power indicator. Of course, it depends if the needle color blends in too well.

[rstofer]

But I guess having two power supplies is good at times for certain things. 

Ah em...  Yes -  two, three, ten, twenty.... some of us feel you can never have too many

Yep, even when we do. This ITT liquidation is really hard on my TEA. But I've not succumb, yet.

Fortunately for me, since I am such an early user, I have excuses since I don't really have any gear :>

Hang around here for another week and you'll need a bigger house!

That power supply should work fine.  In the "Learning..." book, they talk about the Global Specialties PB-503 prototype board and it has a triple output supply like yours but nowhere near as complete.  Like it doesn't have meters... 

http://www.globalspecialties.com/electronics-trainers/analog-a-digital-circuit-design-trainers/item/97-pb-503.html

That should give you a benchmark on the equipment required.  Nothing special...

You could put some inline fuseholders in your power supply leads and get some very low current fuses.  OTOH, there is nothing quite like the smell of magic smoke.

[Berni]

Thanks. I did the the current limiting tests and the ammeter showed the correct current values, according to the instruction manual.

Someone on muffwiggler just shared this mod he did to his 6236B -- smd led lights above the meters.  I so want to do this!  I was thinking about lighting up the meter last night, even before I saw this photo.  Makes it so much easier to read!

IMG

Nice to hear.

That mod does look nice but i would rather use very warm white color LEDs to make it look like its lit by incandescent bulbs as some of these meters used to be. Extra points if you add a soft start circuit to make them slowly fade on.

[bitseeker]

Someone on muffwiggler just shared this mod he did to his 6236B -- smd led lights above the meters.

...i would rather use very warm white color LEDs to make it look like its lit by incandescent bulbs as some of these meters used to be. Extra points if you add a soft start circuit to make them slowly fade on.

Fade on. Nice touch! And dim slightly when the current gets too high?

[JenniferG]

I like the idea of the incandescent look; I'd definitely want that!  All my Philips LED bulbs here have a nice warm color temperature.

Maybe not as bright either.. He put a row of SMD above.  Maybe it needs half the amount.

Looking that photo above and mine, I see that my power lamp doesn't have it's little dome ><

[Cerebus]

I have an HP 6236B in my collection, it's become the everyday PSU because it hasn't got fans - ah, peace and quiet. It's also notable for how electrically quiet it is too. The specs for noise and ripple on any output are 0.35mV rms, 1.5mV peak-to-peak 20 Hz to 20 MHz - confirmed as still in spec on my 1984 vintage model. You'll struggle to find figures as good as that on many modern PSUs - Keysight's newest analogue PSU models come in at 10mV peak to peak.

[JenniferG]

I have an HP 6236B in my collection, it's become the everyday PSU because it hasn't got fans - ah, peace and quiet. It's also notable for how electrically quiet it is too. The specs for noise and ripple on any output are 0.35mV rms, 1.5mV peak-to-peak 20 Hz to 20 MHz - confirmed as still in spec on my 1984 vintage model. You'll struggle to find figures as good as that on many modern PSUs - Keysight's newest analogue PSU models come in at 10mV peak to peak.

Thanks, I'm glad I bought this.

[K5HJ]

I've had one of these for over 25 years and other than replacing an electrolytic capacitor it just keeps on working.
You can short all of the outputs to ground or to each other, walk away and it will not be damaged.
These supplies are bullet proof.

Randy

[JenniferG]

I've had one of these for over 25 years and other than replacing an electrolytic capacitor it just keeps on working.
You can short all of the outputs to ground or to each other, walk away and it will not be damaged.
These supplies are bullet proof.

Randy

I need to learn how to test an electrolytic cap. [Yeah I know how to discharge it -- I usually test voltage after I think I've discharged it just to make sure it is really discharged.  And I never use 2 hands near big caps like that -- don't want current going across my heart.]

I've tested one before but only with a capacitance meter checking the uF only.  I've learned recently that isn't enough and I need a $100 or so LCR meter.

[Berni]

There are capacitor ESR testers out there for quickly checking if a electrolytic cap is at the end of its life.

But you could do it with a oscilloscope too. If you discharge a capacitor in to a low value resistor to create Amps of current flow out of it you can see the ESR in the voltage curve. If the capacitor is good the curve should look close to a textbook capacitor charge/discharge curve. But when there is a lot of ESR on the capacitor the voltage will suddenly jump down with a sharp edge, flowed by that expected smooth discharge curve. That jump is the voltage drop on the capacitors internal resistance caused by the sudden large current. If you measure how big that drop is you can use the value of your discharge resistor and some math to find the internal resistance of the capacitor.

[SingedFingers]

Nice supplies those 6236B's. I did AoE 2nd edition with one in about 1996! Literally just bought it's successor yesterday, the E3630A as I regretted selling it years ago. If you want to get through AoE cheaply you can make do with one supply. I did when I did the old 2nd edition anyway. Had an 8xAA battery box and a croc clip lead as a second supply. If not the new HY1803D linear supplies are dirt cheap and aren't terrible.

Also skip the PB-503 breadboard. Spend the money on a nice sweeping function generator. HP 3312A is spot on for that course.

Incidentally I did the AoE course, then I did an EE degree and the AoE course was far more valuable.

Testing electrolytic capacitors... I'd just ignore this. They are almost certainly fine if the supply is operating correctly. Don't diagnose a problem until you have one.

Don't worry about current limiting to start with at all. There isn't much risk of anything spectacular happening at the supply's hard limit. You can afford to chuck the odd smoked resistor or transistor. It's different when you're dealing with large assemblies or expensive ICs but then you can get some mileage by putting a 100 ohm resistor in series before power up. If that gets hot, something is amiss.