# Help to get a bench power supply:-)

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#### FriedMule

I want to get a bench DC power supply for repairing solid state amplifiers I do not know how many Watt I will meat except I do not calculate on repairing professional stage gear.
I know that you have to be the perfect to ask, because I want to buy a bench DC power supply that shall act as an replacement for the transformer in a amplifier under repair or construction. What DC Voltage range would you recommend and how many Amps?

#### TBTL

It concludes that +- 25 Vdc / 800 mA is sufficient to test most class B (or AB) amplifiers. Make sure the supply has some form of current limiting that can be set at a low value.
What amplifier classes are you repairing? Professional stage gear sometimes uses class H, with multiple rails.

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#### FriedMule

It concludes that +- 25 Vdc / 800 mA is sufficient to test most class B amplifiers. Make sure the supply is adjustable and has some form of current limiting.
Okay I'll read that thanks But you do find amplifier that uses 36V and several amps?

#### ubergeeknz

Okay I'll read that thanks But you do find amplifier that uses 36V and several amps?
Once you've ironed out the bugs on your bench supply, you can hook up the final supply with a good degree of confidence (or via a couple of limiting resistors)

#### amplidude

I use a vario transformer hooked up to a old pa toroidal, and the classic dual bridges and capacitors,
Bulbs in series with its output, for initial testing, it can deliver anything up till +/÷ 95 volts, and the best part its dirt cheap.

#### FriedMule

Yes that's also a possibility. You don't use current limiting or all of the rest?

#### amplidude

The bulbs are the limiting, you could also use resistors, let's say you set the voltage to +/÷ 60 volt and want to limit current to half an amp, just insert 120 ohm resistors, make it more fancy with rotary switch for different limited currents add voltmeter and ammeter,

#### amplidude

Ebay has some programmable dc dc power supplys, some even with USB connectivity so you can adjust and monitor from PC, 600w output, but I'm not sure how noisy theese modules are,

#### Jazid

I've looked around ebay etc and the cheaper options are a low voltage regulated linear (Thurlby thandar etc) with reasonably low noise and typically +-30v 1-2 amp, or a new, smaller, higher power switching PSU still +-30v and noisy as hell, and which may or may not be a death trap. Expensive options are thinner on the ground. If you want a quiet, high voltage, limitable high current bench PSU go empty your piggy bank.
You can usually series or parallel connect decent bench supplies to get more voltage or current, but one has to be slaved to the other for control purposes.

#### FriedMule

On Ebay there is this old fellow: HP Agilent 6574A 60 Volt 35 Amp 2000 Watt Power Supply System.

#### Jazid

What are you going to do? Fix arc welders? I bet that thing will buzz like crazy.
I've got a small early 70s 200V HP bench PSU and it's great, I use it all the time. It also buzzes [emoji4]

#### FriedMule

What are you going to do? Fix arc welders? I bet that thing will buzz like crazy.
I've got a small early 70s 200V HP bench PSU and it's great, I use it all the time. It also buzzes [emoji4]
LOL yes I expect to weld the cabinet together

No I just found that unit, I do not need 200V since I want to use it to replace the build in PSU while testing or building. So the best would be something +/- xxV and xA.

Oh and by the way, I know what the Voltage means for the sound in an amplifier, but what does the Ampere mean for the sound?

#### amplidude

Yes those professional unit can be scary expensive, I have to small variable bench supplies +/÷ 25v and one delta elektronika 60v 10a, I would really like a second delta elektronika and run them in series, but theese units are scarse in my country, they have sockets on rear panel for daisy chaining several units with one as master, external current sensing, very low noise etc.

#### amplidude

On Ebay there is this old fellow: HP Agilent 6574A 60 Volt 35 Amp 2000 Watt Power Supply System.
Think you'll need two of those units for +/÷ way out of my league

#### amplidude

The amps are the ones really driving the voice coils

#### FriedMule

The amps are the ones really driving the voice coils
Thanks for all your reply's, so the current is how hard the amplifiers kick the speaker, or more correct, how hard a grip it has?
But yes 35A may be a tad in the high end, maybe tipping over what you would call sanity?

#### FriedMule

I have for about a week searched the internet for a power supply but I haven't found what I am looking fore, I hope that you will please help.

I don't care it it is one or two units but what I hope to end up with is about this:
linear is prefered

+/-25V 10A and +50V 10A

precision is not so important
Total prize, used or new do I decide later on but not above 2,000\$ new.

#### ubergeeknz

Have you all the other equipment you need already or budgeted for? It seems like spending \$2k on the be all end all power supply is overkill for DIY?

#### FriedMule

Have you all the other equipment you need already or budgeted for? It seems like spending \$2k on the be all end all power supply is overkill for DIY?
You are completely right, and I do not hope ever having to use that much, but I know of some units that mach my wishes for fare above 2K\$.
My reason for such a high prize as max is that I do not want people to eliminate any unit because I did write 1,000\$ or something.

I hope to get the perfect unit for nearly free but that is unrealistic, so if anyone knows of a model, then just tell

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