50 watt wiring question

Trem Abuser · Post by **Trem Abuser** » Sun Feb 27, 2005 1:16 pm

I'm looking at the WIRING GUIDE: 50 WATT sheet from the Metroamp CD. I'm also looking at the picture of the board with the written description of which which wires get connected where. (And the schematic, but I'm still having trouble seeing how the schematic tells me how to wire my amp...)

I'm specifically referring to the upper right hand corner of the board where, according to the picture, a "red, small red & small white wires to output trans, fuse holder and choke" apparently connect.

First of all, is there any component on the board that those wires are connecting to? Or do they just join together at that point?

Next, I thought the choke connected to the 1/2 amp fuse holder along with the OT primary wire. Is the reason the three wires connect at the board simply one way to connect the fuse holder to the choke and OT primary (and only have one wire going to the fuse holder)?

Gonzo · Post by **Gonzo** » Sun Feb 27, 2005 4:35 pm

I may be wrong but I think that's just a turret to join everything on.
I just hung everything on the fuse instead.It was easier for my parts layout.

The schematics aren't that hard to read once you get in to them.
Look at the 1987 schematic, The B+ comes off the two diodes then goes to the two 50Uf + sides of the Filter cap then to the fuse and then to one side of the choke.The other side of the choke continues on to the 10K resistors.

Hunt up as many pictures as you can to help with the wiring.
You should get used to using the schematic.I picked out a few mistakes in the 50 Watt files last month.George probably fixed them by now but it's still a good idea to use the schematic.

Flames1950 · Post by **Flames1950** » Sun Feb 27, 2005 5:38 pm

Yup, just a convenient junction point.

Trem Abuser · Post by **Trem Abuser** » Tue Mar 01, 2005 6:57 pm

I purchased all new pots as part of my project. The baggie the pots came in included 6 of those caps which are shaped like a molar tooth, and I believe their values were 100, 250 and 500.

I did not see that small can-shaped cap which (the 100W instructions say) is soldered to the presense control (I believe, I don't have the materials in front of me now), and I forget what value that cap is.

Is the cap on the presence pot one of those caps which came in the baggie, or do I have to purchase that can-shaped capacitor separately?

Flames1950 · Post by **Flames1950** » Tue Mar 01, 2005 7:20 pm

Typically it's a .1uF (sometimes you'll see a .68uF, but that's usually a different circuit with an extra resistor.) You'll have to get one, it's not one of the ones with the pots. Those are just for trying different bright cap values.

Trem Abuser · Post by **Trem Abuser** » Wed Mar 02, 2005 11:01 pm

And is that .1uF cap a special type (a "sozo" or something)? Or can I pick up and .1uF value cap from Radio Shack?

Flames1950 · Post by **Flames1950** » Thu Mar 03, 2005 8:30 am

Usually everyone uses a SoZo or Mallory for it. Radio Trash probably only has ceramic disc or funky blue polyester caps.

Trem Abuser · Post by **Trem Abuser** » Sat Mar 05, 2005 3:07 am

Flames1950 wrote:Typically it's a .1uF (sometimes you'll see a .68uF, but that's usually a different circuit with an extra resistor.) You'll have to get one, it's not one of the ones with the pots. Those are just for trying different bright cap values.

And I assume a 1uF Torres orange drop cap would not work in a pinch, would it? (Of course I have one of these laying around, but no .1uF caps.)

Flames1950 · Post by **Flames1950** » Sat Mar 05, 2005 7:49 am

It will work, although I don't know what effect it will have on the presence control's range. But it can go in to get you rolling until you get the right cap.

Trem Abuser · Post by **Trem Abuser** » Thu Mar 24, 2005 8:13 pm

On my amp, it was 6L6 powered before, and pins 1 and 8 of the output sockets were jumpered and grounded. I did not install the 1 ohm resistors since I did not have any and did not order any.

Can I leave the pins jumpered and grounded, or should I change that?

tooloud · Post by **tooloud** » Thu Mar 24, 2005 8:38 pm

yes, leave them like that till you get the 1 ohm resisters.

Guest · Post by **Guest** » Fri Mar 25, 2005 4:31 am

Ok, thanks.

The Metro 50 watt wiring guide shows a 27k resistor right next to the rectifier diode assembly. The notated picture of the 50 watt, with the values of the board components, shows that same resistor to have a value of 220k, and a piece of bus wire connecting one of the posts that the 220k resistor is attached to to the post that the "lower left" rectifier diode attaches to.

The wiring guide does not show this short piece of bus wire.

Which one is correct?

tooloud · Post by **tooloud** » Fri Mar 25, 2005 7:38 am

the 100 watt has a bias tap from the PT and uses the 27k. the 50 watt takes its power from the high voltage off the diode from the standby switch and needs the bigger resister 220k to take the voltage down...

Guest · Post by **Guest** » Fri Mar 25, 2005 3:28 pm

Thanks guys. Another few....

1. The wiring guide also shows a black ground wire coming off the bottom of the board between the Vol. 1 and Treble pots (on the diagram) and going nowhere (to ground). Does this wire get attached to the bus wire on the pots?

2. The wiring guide shows a pink wire coming off the lower right side of the board going to the Power Transformer. Where does that wire connect?

3. Billy, if you see this one - the power diagram you e-mailed, looking at the filter cap connections immediately to the left of the bias pot, your diagram has the filter cap and choke connecting to the northern side of the board to the 10k resistor, and the other side of the filter cap connecting to the 10k resistor on the southern side of the board.

The Metro wiring guide shows one wire from the filter cap to the northern side of the board and three wires (choke, filter cap and output tube pin 6) connecting together on the southern side of the board.

Can both ways be used?

tooloud · Post by **tooloud** » Fri Mar 25, 2005 4:38 pm

the black wire is going to the pot's ground buss.......the pink wire is from the PT on the 100 watt but not the 50 watt.

Metropoulos Forum

50 watt wiring question

50 watt wiring question

Capacitor across presence(?) control