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[Art Welter]

I dunno.  I think they did voltage first.  How else would you explain the presence of three 10uF caps with three different voltages?

Scott,

I got out the big magnifying glass and read the actual capacitor values on my 277-1008C (the schematic was for 277-1008B...) and there are four 10V caps with three different values:

R.S. Mini Amp 277-1008C actual cap values:

   C1   “101”    (ceramic disc)
   C2   4.7μF    50V
   C3   “220”    (ceramic disc)
   C4   4.7μF    50V
   C5   22μF    16V
   C6   220μF    10V
   C7   100μF    10V
   C8   220μF    10V
   C9   1μF       10V
   C10   “101”    (ceramic disc)

 It does appear the schematic puts the voltage first, then capacitance, but the actual values make me suspect  the schematic cap values, seems some may be missing  a decimal point.

Art

 

[Ike Zimbel]

Scott,

I got out the big magnifying glass and read the actual capacitor values on my 277-1008C (the schematic was for 277-1008B...) and there are four 10V caps with three different values:

R.S. Mini Amp 277-1008C actual cap values:

   C1   “101”    (ceramic disc)
   C2   4.7μF    50V
   C3   “220”    (ceramic disc)
   C4   4.7μF    50V
   C5   22μF    16V
   C6   220μF    10V
   C7   100μF    10V
   C8   220μF    10V
   C9   1μF       10V
   C10   “101”    (ceramic disc)

 It does appear the schematic puts the voltage first, then capacitance, but the actual values make me suspect  the schematic cap values, seems some may be missing  a decimal point.

Art

I can't quite figure out your references (C1, C2 etc.) against the schematic, but the only two caps that you would have to change to a higher voltage rating are the two de-coupling caps. These are the ones that go across the power supply rails (+ to 0v) and are called out as "10/22" on the left side of the schematic and "10/47" on the right side. The values of those caps are not super critical, but to mirror what's already there you would need a 22uf -16/25/50v (any of those voltages will work) and 47uf in the same voltage ranges. Electrolytic or tantalum caps will work...make sure you get the polarity right when you put them in or they WILL blow up. Or, just go with higher voltages with all four of the 10v caps. I'm awash in capacitors here...PM me and I can pop them in the mail for you.

[Russell Ault]

I can't quite figure out your references (C1, C2 etc.) against the schematic, but the only two caps that you would have to change to a higher voltage rating are the two de-coupling caps. These are the ones that go across the power supply rails (+ to 0v) and are called out as "10/22" on the left side of the schematic and "10/47" on the right side. The values of those caps are not super critical, but to mirror what's already there you would need a 22uf -16/25/50v (any of those voltages will work) and 47uf in the same voltage ranges. Electrolytic or tantalum caps will work...make sure you get the polarity right when you put them in or they WILL blow up. Or, just go with higher voltages with all four of the 10v caps. I'm awash in capacitors here...PM me and I can pop them in the mail for you.

Wouldn't it be easier/safer to pop a DC-DC converter into the battery compartment and give it the 9V it wants? Could be as simple as one IC with a couple capacitors soldered to the leads.

-Russ

[Art Welter]

Wouldn't it be easier/safer to pop a DC-DC converter into the battery compartment and give it the 9V it wants? Could be as simple as one IC with a couple capacitors soldered to the leads.

-Russ

Russ,

Yes, the 12v to lesser DC-DC converters available for under $5 would work fine- I'd wreck something trying to replace those little capacitors, speaker crossovers are as small components as I can deal with comfortably.
I have two unused DC-DC converters that go the other direction, can't even remember what I bought them for...

Art

[Jeff Robinson]

Russ,

Yes, the 12v to lesser DC-DC converters available for under $5 would work fine- I'd wreck something trying to replace those little capacitors, speaker crossovers are as small components as I can deal with comfortably.
I have two unused DC-DC converters that go the other direction, can't even remember what I bought them for...

Art

How about a 7809 regulator? Or is that too last century?
https://circuits-diy.com/9v-power-supply-circuit-using-lm7809-voltage-regulator-ic/

2 x .01 mFd capacitors and a heat sink, should not need a lot of heatsink to dissipate about 3/4 watt (150mA x 5V).

Jeff Robinson

[Russell Ault]

How about a 7809 regulator? Or is that too last century?
https://circuits-diy.com/9v-power-supply-circuit-using-lm7809-voltage-regulator-ic/

2 x .01 mFd capacitors and a heat sink, should not need a lot of heatsink to dissipate about 3/4 watt (150mA x 5V).

I suppose it depends on the application, but when dealing with battery power I tend to assume that "more efficient" = "better". With the DC/DC converter there's also typically no need for a heatsink, so the BOM is slightly shorter, too.

-Russ

[Art Welter]

I suppose it depends on the application, but when dealing with battery power I tend to assume that "more efficient" = "better". With the DC/DC converter there's also typically no need for a heatsink, so the BOM is slightly shorter, too.

-Russ

Exactly- the whole idea was to eliminate anything that sucks power from a 12v 55 watt hour battery source also powering a little 2 x 10 watt amplifier.

Short of plugging in to the 12v directly (I have the adaptors) a DC/DC converter is the simplest to wire, and cost less than 9 volt batteries.

[Helge A Bentsen]

FWIW. Could you use something like this?
https://www.ebay.com/itm/253114270412

Bought one for my kitchen stereo, I'm powering it off some random DC adaptor I found in a box full of "stuff", it's 15V or something. Don't remember exactly. Sounds good, doesn't get hot but get's plenty loud.

[Russell Ault]

FWIW. Could you use something like this?
https://www.ebay.com/itm/253114270412
[...]

I'm guessing not, since one of the defining features of the RS Mini Amp is the built-in speaker...

-Russ

[Art Welter]

I'm guessing not, since one of the defining features of the RS Mini Amp is the built-in speaker...

-Russ

Russ,

I actually seldom use the 16 ohm speaker, use the RS Mini amp as a pre-amp.
Have some 12v Class D amps similar to what Helge posted that would use the RS mini amp for a pre-amp.

Art

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