On Sat, 18 Feb 2017 10:33:47 -0500, "Michael A. Terrell"
wrote:

Tom Biasi wrote:
On 2/17/2017 9:37 PM, wrote:
I picked up an old tube type Eico 320 Signal Generator. I'm tracing it
and checking stuff. There was a disconnected paper (.5mf 450V)
capacitor. The tube filaments and pilot light work. There is B+
voltage, The voltage from the 6X5 tube at the filter cap, is around
140VDC. (That seems low). The AC volts on the transformer secondary is
about 450V (or 225V each side of the center tap). There is a 2watt 5000
ohm resistor which comes from the power supply, which feels warm, so
apparently there is a voltage draw.

Anyhow, I have found three schematics in PDF format, an one as a .GIF.
They are probably all from the same source, and are very hard to read.
The parts symbols are ok, but where it says the cap and resistor numbers
(such as is that C8, C6 or C3), I can not make out the numbers. They are
blurry. I've tried several pairs of reading glasses, enlarge and shrunk
the diagrams on my screen, and they are just plain poorly scanned.

Does anyone have a decent schematic? And one that shows the voltages at
the tube contacts would greatly help too.

I intend to recap this thing, but first I need a useable schematic.

Thanks

BAMA has it in djvu format.


Sadly, it is the same scan and resolution as the PDF file. It is
typical of the quality of what Eico supplied with their kits

So you looked and saw the same thing. Thank You.
It seems that from what you said, the original was a lousy print job,
and I'm sure scanning it just made it worse. A few of them numbers look
like nothing but an ink blob. Those numbers should have been larger
right from the start. There is plenty of white space to have made them
larger.

Fortunately there are only 12 caps and 9 resistors. (The other part
numbers are not important and are obvious). The good thing is that it
seems that C3 is near C4, near C5 etc. I'm just redoing the (GIF
version) of the schematic using my paint software, and putting in bigger
numbers. When I finish, I will have a better schematic. And I am
checking each one against the actual circuit.

For those of you who work on a lot of this tube equipment, does it seem
that 140V B+ is low? It does to me, with 450V AC coming from the power
transformer, but it's been many years since I worked on this stuff. The
'lytic cap is not shorted according to my VOM. I checked that before I
plugged it in. I will have to check the tubes too, but I dont have any
tube tester yet. (I have one somewhere). [whatever happened to the good
ol' drug store testers]

At least there has not been any smoke!!!

I'll have to order all new caps as soon as I confirm the numbers are
correct. Just curious, what would you use for that filter cap "lytic?
The schematic says 16mf or over (weird). I'm thinking 20 to 30....
(I cant read the original, since it's numbers are not visible, and it's
in a spot making it hard to rotate without removal.

Either way, it feels good getting into a tube device again.....