A470 Lead I.D.

[Geezer]

Some time back I made a score at an estate sale--the deceased was a diy'er and left a box of Dynaco transformers and gutted chassis': An ST70, four Mark 4's, two Mark 3's. an ST35, a pair of SCA35's and two PAS3X preamps. The seller asked for $50 but for the sake of Karma I told him they were worth more and gave him $100. I should have given him more, a week later I sold a single Mullard KT88 from one of the Mark 3's for $140 on Ebay.

The cloth-lead trannies are so old that the color has faded from nearly all the wires--I can't tell blue from green or yellow from red or orange. The lead length is no help. Right now I'm working on a pair of ST70's (using new PA-060 PT's and A470 OPT's from two Mark 4's, the best external condition of the lot). I'm sorting out eight A470 OPT's, only two of which have visible color (but the good ones provide a visible reference for the others). All I can tell is which leads are solid color, which are striped and whether they're a dark or light color.

What's the simplest way to identify the blue/green/striped-blue/striped-green/yellow/orange/brown/red wires? Just remove the bell and note the position of the taps compared to a schematic? Does anyone have a procedure for pinpointing by measuring resistance or inductance between leads? Finally, is there a way to test the OPT's out of circuit to verify they're good (or at least not DOA) before I start soldering?

[Geek]

Hi,

If you remove the bell, you should be able to see the preserved colour of the leads.

Be careful though... I have yet to have a "dipped" A470 and all the E and I lams will likely fall out

Cheers!

[burnedfingers]

Been there done that. Removing the bell housing shows the original colors enough to figure what is what. One can also ohm it out I suppose.