Re: R7 parent board pin out
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Many thanks for the info Jim.? I have a spare Regulator Board, which currently does not work in my R7....? And a newer version power supply board.? My R7 has the older one.? Will the new one work in an older R7?? I don't want to destroy?anything by trying to use this newer PS board.
BTW, today I replaced the regulator board's 4700 uf cap and now my voltages are closer to correct.? Over 12v? out of the regulator board and 10.3v on the 10V rail on the PS board.? I think this R7 has had PS problems in it's past.? Four of the pins on the regulator board have been very hot because the molex connector has turned brown there.
Thanks again for your help.
73, Dan (W3DF)
On Mon, 28 Apr 2025 00:58:03 -0400
"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.
The 220uF on the PS board will run warm because it is essentially filtering square wave ripple from the mutltivibrator oscillator. That's why I recommend a high quality 105C cap. Harder to find in axial, but possible. I would use a 35V part.
It almost sounds like something is drawing too much current. Do you have a scope? If so, check for excessive ripple at the output of the bridge rectifier. The variable regulators on both boards are bog standard 723 circuits which are mature technology. Barring component value drift you should be able to dial in the voltages with no trouble. As has been said, check your Molex connectors thoroughly. Unplug the Power Supply board and see if you can adjust the Regulator to spec. You can also try running the rig from external DC and see if you can net the +10v.
> Are the old and new version power supply boards plug-in compatible?
Yes.
> 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.
That could be spurs from the 23 KHz multivibrator oscillator on the PS board. Usually they are about 23 KHz apart and will wander a bit.
I am attaching the PS board BOM per your request. I did notice one thing I had not seen before. My R7A has the late version board so I had not looked at the early board much. There is an added capacitor on the schematic that is not present on the TR7 version of this board, C1919. It is shown as a 1000uF from the primary center tap of the transformer to ground. It is NOT listed on the BOM on shown in the pictorial. Which makes me want to open up another R7 so see what is there. If you do have that capacitor it should he replaced as well by the same logic as C1908, as it has been worked hard. If you don't have it, don't worry about it at this point. It is either a late addition or an artifact of a part that was removed from the build. We don't know which at this point and TR7 boards seem to work fine without it.
It is also worth noting that the PS board has two independent ground circuits which connect to the parent board. You have one ground for +10/+5, and another for the +24/-5. Check both.
--
73
-Jim
NU0C
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