quad fm1 power supply

[6B4G]

Hi guys I have just picked up a Quad FM1 and I'm looking to build an external power supply for it,
does anyone have any ideas?
I have on hand a 250-0-250vac 100mA + 6.3vac 2A transformer
would this work ok
The info I have is that the radio needs B+ 330v @ 30mA and 6.3Vdc @ 1.5A
As I am shocking in designing power supplies could I get some help?

[DeathRex]

The FM1 didn't come with a power supply? You can use Duncan's PSU II to make a power supply.
This will get you about 305VDC. You can also use a 12X4 or 6BW4. For move voltage use a 6V4, or for even more use a 6CA4. Or use UF4007s for about 340VDC.
AC on the filaments will be fine. For a choke you can use 0.5H to 20H. You can use a resistor instead of the choke, but to get the AC filtering performance, you will loose a bit more DC voltage. A 330 ohm-1 watt will filter almost as well as a 1 henry choke, but you'll loose another 9 volts. Might need to increase the second capacitor to 100 or 220uf or whatever you have. For better filtering you can add another resistor and capacitor; a CRCRC.

[6B4G]

Thanks Rex for the reply, I just had a look at psu ii and I ran some simulations.
I'm not sure but I have added the sim bellow.
What I have as tested: power transformer rated at 250-0-250 100mA
My wall voltage is 230VAC
Measurements: PT= primary resistance 59.4 Ohms
Off load secondary = 261-0-261
Secondary resistance = 193 ohms to center tap (385.6 ohms across)
I also have a Hammond 156R choke: 1.5H @ 200mA 56 Ohms
lots of caps to use but I thought a 32uF + 32uF 500v would be ok.
If I have added the correct values I see a 312v supply with a 0.3v ripple
Please can you tell me if I'm in the right path?

[6B4G]

Another thing is that the cable that is attached to the tuner is a three core
one for the B+ and two for the 6.3Vdc
I don't get it but do I send the B+ without its ground?

[DeathRex]

This says it has a 4 pin cable. And PL1 the audio connector seems to be the only connector to ground. Wonder if it switches ground?
http://www.vintageaudiorepair.nl/quad/u ... 1_rev.html

[6B4G]

You are correct it has a 4 pin plug but only 3 wires. As you can see Red Green Black.
The other cable is the audio out and its gnd is the only earth to be attached.
I was thinking to change the cable from a 3 wire to a 4 wire and bring in the ground like that.
Will this cause a ground loop? I don't know.

[DeathRex]

It should. Where does the orange wire go that's attached to the brown wire, since the brown wire is a shield, it should also be a ground. Is the schematic correct, so that one side of your filaments grounded, so you have B+, filaments, and ground?
And where does the shielded part of that shielded wire go?
Your schematic says it's for serial number 19062 and above, does your serial number fall there?

[DeathRex]

Looking at the Quad 22 preamp schematic, it looks like one pin has B+ on it all the time, another pin gets B+ switched on whenever Radio 1 or Radio 2 are pushed on, and the other 2 pins get filament voltage.

http://www.geocities.ws/quad_esl63/imag ... reqcii.jpg

[6B4G]

You are correct but are we to assume (no pun intended) that ground then is passed threw
the audio in cable?
Also looking at the schematics there are no references to the filament if they are AC or DC.
I have been told that they are DC and I think that + is on pin 1 and - on pin 2.

[DeathRex]

The filaments are AC, you can look at the Quad 2 power amp, that all this seems to get their power from: Quad 2 to Quad 22 to Quad FM1.
If you have a ground on the power cable, then you don't want both sides of the audio cable grounded.

[DeathRex]

If you aren't going to use it with a Quad 22, then I would just remove, but keep, the 3 wire cable, and install a 4 wire cable to your new power supply.
Or this could be a good time to replicate a Quad 22 and 2 X Quad 2. The Quad 2 would be easy, and the Quad 22 will have about the same case as the FM1 but with 4 more knobs, and different innards. Of course if you can find a Quad 22, there's one on ebay.com now for $114, it will make your job easier.
For some reason there's a English power cord there?

[6B4G]

I'm going to use it on a Leak Varislope Stereo preamp with the Stereo 50 Power Amp that I
just finished restoring, I have two Quad FM1s, one for parts and the other for repair not that it needs anything
apart from a power supply. The purchasing of another unit just isn't in the budget.
I know that I might be opening a can of worms but it is also a challenge, the grounds seem to be
the biggest problem, not the adding but will they cause any advert fault?
On the other hand if I was using a LEAK TROUGH-LINE ll it would be the same, so there shouldn't be
a problem.

[6B4G]

Checking threw the schematics of the Quad ii power amp I see that the plug going to the control
unit has pins 1 and 4 ground pin 2 input pin 3 B+ 330v 17mA pins 5 and 6 6.3vAC.
Control Unit Quad 22 Radio 1 and 2 power outlets get the B+ 330v 17mA on pin 2 of the 4 pin plug
going to the FM1 Tuner and pins 1 and 2 have the 6.3vAC
So from what I can see all voltages are from the Quad ii and the heater voltage is ac and not dc
the B+ 330v is 17mA and the ground folows from the power amp to the control unit and tuner gets it
ground from the audio input. How bizarre.