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Author Topic: Looking for Collins MP-1 DC supply transistors  (Read 4091 times)
KH6VP
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« on: August 27, 2017, 11:38:00 AM »

Hi,
I have an MP-1 DC supply which I would like to repair and want to replace the transistors. These are DA3F3, that come in a MT-7 case. Does anyone have any spares? There is nothing equivalent [many exist with similar specs but not this case style].
Thanks,
73s, Peter, KH6VP
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N4MQ
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« Reply #1 on: August 28, 2017, 06:01:23 AM »

Have you seen this site?

http://www.weisd.com/test/GenericParts_WEISD_view.php?editid1=DA3F3

Enjoy, Woody
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KH6VP
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« Reply #2 on: August 28, 2017, 08:41:53 AM »

I don't know why people suggest this because the cases are completely different. The screw support of the NTE213 is between its legs and the support of the DA3F3 is on the other side. The DA3F3 was made for the Military and is an MT-7 case. Which is why I asked. Thanks.
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KC4ZGP
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« Reply #3 on: August 28, 2017, 09:14:07 AM »


The 2N3771 is a fine high current, high frequency transistor. Make it fit.

Kraus
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W1BR
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« Reply #4 on: August 28, 2017, 01:01:16 PM »

Kraus

Do you ever have anything of value to add to these threads?  The original part is a scarce PNP germanium power transistor...  subbing a silicon NPN part is not trivial and would take more than "making it fit."
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G3RZP
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« Reply #5 on: August 29, 2017, 02:09:58 AM »

FWIW, Wholesale Electronics Inc  (800-351-2233) claim to have an equivalent part NTE 213 at $58.80 each. The drawing shows the very old can style, so they may be correct.

see http://www.weisd.com/test/GenericParts_WEISD_view.php?editid1=DA3F3

GL es 73

Peter G3RZP
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VE3YF
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« Reply #6 on: August 29, 2017, 06:29:14 AM »

Kraus

Do you ever have anything of value to add to these threads?  The original part is a scarce PNP germanium power transistor...  subbing a silicon NPN part is not trivial and would take more than "making it fit."

Peter:

Substituting a $4.00 transistor for a $50.00 transistor is the extent on wizardry and knowledge from Kraus. I have yet to see something constructive and useful to offer from this guy. One dumb comment after another.

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73 De Mike
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http://www.ve3yf.com
KC4ZGP
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Posts: 1961




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« Reply #7 on: August 29, 2017, 09:59:33 AM »

Hi,
I have an MP-1 DC supply which I would like to repair and want to replace the transistors. These are DA3F3, that come in a MT-7 case. Does anyone have any spares? There is nothing equivalent [many exist with similar specs but not this case style].
Thanks,
73s, Peter, KH6VP


Hey Pete,

Here's an idea. You need two high current transistors which switch as fast as an RF signal eh? Look into the MRF series
available at RF Parts. Lots of options. Give them a call. Give them your specs.

A transistor is a switch. Some move fast. Others faster. Of the thousands available, I'm sure you'll find something and
if you have to modify, then modify.

Marconi, Tesla, Edison, etc. didn't have Mouser's, Digi-Key, RF Parts. They made, they modified.

Kraus
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KC4ZGP
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« Reply #8 on: August 29, 2017, 11:01:58 AM »


Herr Pete,

I found this.

http://dilp.netcomponents.com/cgi-bin/nteinc.asp?partnumber1=NTE213

My computer hasn't Adobe so I cannot download specifications, prices etc.

Good luck.

Kraus

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N4MQ
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« Reply #9 on: August 29, 2017, 02:05:50 PM »

ebay has one for sale MP-1, from the photos the design is really dated and a museum piece.  Maybe an inverter of 12 v would be a better option, the line up of power packs have fallen in price and grown in power output. Woody
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KH6VP
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« Reply #10 on: September 22, 2018, 05:25:06 AM »

I have found replacement transistors and now I own three working MP-1 power supplies. I also own two 516E-1 mobile power supplies originally made for the KWM-1 but they can also be used for the KWM-2.
I decided to collect mobile power supplies from the 60’s so if anyone has any, let me know.
My EICO 752 mobile power supply is interesting and so is the WRL/Galaxy 384. The eico uses a small toroid transformer for feedback and a regular transformer for power, while the 348 uses one large toroid that can handle up to 300watts. Back in the 60’s, large toroids were expensive. The 516E-1 uses a small toroid for feedback while the MP-1 uses one large toroid to handle both feedback and power circuits.
Peter
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G3RZP
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« Reply #11 on: September 23, 2018, 01:09:50 AM »

The use of a feedback transformer was fairly common: it had a core that saturated easily and was somewhat more expensive than the toroidal core for the main power transfer.

Somewhere I have the mobile supply for the Drake TR3 - but I don't know where.

Replacements for Germanium switching transistors aren't easy to find. In some cases, it might be possible to build a driver that can take the current drive for switching bipolar transistors and amplify it to sufficient volts to switch MOSFETS. Choosing ones with very low rds on could give better performance than the germanium bipolars with their somewhat higher Vcesat.
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KX4OM
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« Reply #12 on: September 25, 2018, 05:33:41 PM »

It might be useful to look at the changes from the Heathkit HP-13 series supplies. They changed the transistor for the A, and changed the circuit substantially for the B. That one has a switching design that I have not seen elsewhere; it is not symmetrical. I have a 13 and a 13B opened up on my bench for capacitor replacements. The transistors in the later models can take higher supply voltages, while the HP-13 is limited  to 14 vdc. The modifications to the base HP-13 design by Heathkit engineers using the same toroidal transformer looks like some experimental work was done, and more may be possible.

Ted, KX4OM
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