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 Post subject: Hp 651a power supply
PostPosted: Jan Wed 13, 2010 3:28 pm 
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Joined: Aug Tue 26, 2008 1:29 pm
Posts: 129
Location: Omaha, Ne
I just can not brake this week
I am working on a HP 651a signal gen. It looks like the a transistor in the -24 vdc power supply is bad
Its a 2N398A pnp Germanium transistor
Any ideas about finding a replacement
Thanks
Steve

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 Post subject:
PostPosted: Jan Wed 13, 2010 10:33 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Albuquerque, NM 87123
It's not listed in NTE. What case style is it? You may have to use a 121 or 104 as a sub and change the mounting.


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 Post subject:
PostPosted: Jan Thu 14, 2010 1:14 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 197
Location: Wayside, NJ Monmouth
Good evening Steve, I was able to find a referance in the Motorola HEP Cross referance spring 1973 edition. It crossed over to a HEP 239, TO-5 case, Ge, Genreal Purpose Power Transistor, 100 Volt 3 Amp., with the collector connected to the case Hope this helps.


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 Post subject:
PostPosted: Jan Thu 14, 2010 3:49 am 
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Location: Pocasset, Cape Cod, MA
150mW, 200mA, 105V, hfe 65, TO5. From the 1981 D.A.T.A. transistor book.


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 Post subject:
PostPosted: Jan Thu 14, 2010 4:05 am 
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Location: Cambridge, Massachusetts, USA
You can buy a replacement here:

http://www.talonix.com/shop/item.aspx?itemid=2723

-Matthew D'Asaro

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 Post subject:
PostPosted: Jan Thu 14, 2010 5:05 am 
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Joined: Oct Sun 15, 2006 12:57 pm
Posts: 3774
Pricey, but you can get them here as well

Mike


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 Post subject:
PostPosted: Jan Thu 14, 2010 2:39 pm 
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Joined: Aug Tue 26, 2008 1:29 pm
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Location: Omaha, Ne
Case is a TO-39 ? TO-5 ?
Steve

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 Post subject:
PostPosted: Jan Thu 14, 2010 9:38 pm 
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Joined: Oct Sun 15, 2006 12:57 pm
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Steve,

Its a TO-5.

Actually, so long as that transistor is not part of the reference comparator you could most likely use a silicon device of similar ratings with no problem.

I looked for a schematic of the 651 PS but couldn't find it on line. The 652 is on bama and I suspect your PS is very similar.

Mike


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 Post subject:
PostPosted: Jan Fri 15, 2010 2:47 pm 
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Joined: Aug Tue 26, 2008 1:29 pm
Posts: 129
Location: Omaha, Ne
Mike
I tried to replace the transitor with a silcon pnp, It wasnt pretty.
I have dug around in all my old junk and found, ZIP.
Had to give in and order a replcement transistor. Shipping was a killer. $6.00

I cut the -24vdc power supply lose and powered the gen. with a external power supply. Ha, kinda works.
On every range setting of the gen. it works from 10- 8 on the range knob. Lower then that it dies off

The 652 on bama is very close to the 651
Later
Steve

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