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Thanks for the info Jim.

Dan (W3DF)

On Mon, Apr 28, 2025 at 12:58?AM Daniel W3DF via <danflan49=[email protected]> wrote:

Yes... I replaced the 220 uf on both the regulator board and the power supply board today.? I am also going to replace the?4700 uf capacitor.? Changing the 220s did not change any of the voltages... still 11.8v instead of 13.8v and 11v instead of 10v.? The caps run warm, especially?the 220 uf on the power supply board, it gets a little hot. I cannot get the voltages right with the adjustment pots.? I checked the resistors on the regulator board and they are OK and I think the pot is OK too.? I turn it fully clockwise to get 11.8v.? Does line voltage affect this much?? I'm running it on 115vac? Since I cannot get the power supply board out I cannot get to the resistors.

Yes...? the power supply board does pull straight up, but only about an 1/8 inch, then it won't go any farther.? I checked for interference but didn't see any.

Are the old and new version power supply boards plug-in compatible?

The R7 works fine the way it is, but there is one strange problem... on the BC band switch positions I hear this randomly wandering heterodyne on several spots on the dial that interferes with?weaker?BC signals.? Sometimes it will wander off to another frequency.

I had WB4HFN go over this R7, but he did not find all the problems.

73, Dan (W3DF)

On Sun, Apr 27, 2025 at 11:56?PM Jim Shorney via <jimNU0C=[email protected]> wrote:

On Sun, 27 Apr 2025 23:15:00 -0400
"Daniel W3DF via " <danflan49=[email protected]> wrote:

> My service manual shows the newer version of the power supply board, but
> the board in my R7 has the two bipolar transistors, I think I need the
> schematic for the older version.
> The board in my R7 appears to be modified but I'm not sure since I don't
> have the schematic, it has components on both sides of the board.

Both versions can be found at the link I posted earlier. Added components are not uncommon on Drake boards.

/g/DRAKE-RADIO/files/R7%20Files

I am attaching a pictorial of the early board.

> Are the two versions plug-in compatible?

Yes.

> I have the newer power supply
> board that I purchased and the regulator board also.? When I plug in the
> regulator board I purchased, the R7 motorboats.? It looks identical to the
> one I have in the R7 that works.? Guess it has a bad component(s).

That is the risk of buying used boards. Now you have another board to repair. Motorboarding is indicative of a failing capacitor. The R7 power supply section is known to be a high heat area when run from 120VAC.

> One other thing... I cannot get the power supply board to pull out, it only
> pulls up a little bit then stops.? I don't know what is stopping it, I
> don't think it's the pass transistors on the side wall.
> I don't want to force it and break something.

It should pull straight up and out but it it has never been removed the Molex connectors could be still very tight.

The old version board should have C1908 (220uF) replaced. That can solve some strange problems. The new version will need all the 10uF caps in the output of the TDA-2002 and the voltage multiplier and the 1uF on the input of the regulator replaced. They have all likely seen life, or close to it. Again, use NEW high quality 105C parts/

--

73

-Jim
NU0C