APD-8025H Color Codes

[Richs1979]

APD-8025H Color Codes wrong
Does anyone know the proper color codes for an APD-8025H output transformer's secondaries? On the online Amp Parts Direct site it shows as brown being common. When it should be black. Originally I wired it according to that diagram thru a 3-way switch. Only a very faint signal. I disconnected all the wires and rigged up a spare output jack with black as common and brown as hot. It worked. Same with yellow and green as hot with black as ground. Is anyone familiar with this transformer and the proper color codes for 4, 8, and 16 ohms? I use a test tone generator with a 1k signal. And I have a Variac. But have no idea how this is done. Help needed. Thank you in advance.

[uki]

Easy way is to read the resistance with multimeter, turn amp off, disconect the speaker,  the smaller resistance is 4ohms.

[shooter]

shows as brown being common. When it should be black.

where did you find "it should be black"??

[Richs1979]

As I stated in my 1st post, hooked up to the switch I had brown as common. Very faint volume in all settings. Everything leading to the output stage measured fine and wired correctly. I pulled the wires off the switch and rigged up an external jack. Hooking up black to ground and brown to tip. It worked. Volume like it should be. Boost switch working, and quiet idle. I then pulled the brown from the tip and hooked up yellow in place of it. It worked again. Green is left but I'm sure it'll work also. So now I need a way to decipher what the impedances are before hooking them back to the switch. If black is not common, then how did the brown and green wires work along with it? I'm hoping this was the problem. The switch checks out. I could be wrong that's why I'd like to verify what is common for sure, and what the other colors are. The only other issue would be a shirt to ground via the mounted output jacks. I'll be be checking this all out this evening. Hope it all works out

[shooter]

hooked up to the switch I had brown as common.

my guess is you wired the switch wrong, not that the switch was bad.


usually the manufacturer's diagrams are correct.


since you have a variac  you could disconnect ALL the OT wires, set the variac to say 3-5VAC connect BROWN and 4 ohm tap, measure primary outside 2 leads, power-down, disconnect 4 ohm and re-connect 8 ohm, power n re-measure.  Each measurement should be a bigger VAC.
**NOTE** an OT IS a step-down so 5VAC on secondary could be in the hundreds of VAC primary, make sure you meter can handle 600V

[Richs1979]

Thanks for the reply. When I started this thread I felt like no one was out there. I'm still green at all this since till this past year, I never built an amp before. Before I pull out the old Variac I did a quick check on the jacks. Walla! One of the jacks was shorted to ground. Stupid mistake. I then did a quick read on my meter. Hers what I got.
Brwn/Blk=1.1 ohm
Brwn/Yellow=1.2 ohm
Brwn/Grn=1.6 ohm

Blk/Brown=1.1 ohm
Blk/Yellow=0.8 ohm
Blk/Grn=1.0 ohm

It should not of worked with yellow and black, but it did. 

[shooter]

Blk/Yellow.... why not, there's just some length of coiled wire between them, which should have ohms


your 1st reading appear to follow what the manufacture shows

[Richs1979]

I feel 100 lbs. Lighter. Mowing the lawn right now. But seriously thanks for the heads up. I'll be rewiring the whole mess this evening. This thing is loud from what I heard so far. Thanks again.
I'll post my results this evening. 😎

[Richs1979]

Wires back where they were. Fixed the grounding issue. Been running the amp now for over an hour. Can imagine what it sounds like thru a 4 x 12 instead of a crappy little PA monitor. Voltages were 438v for both el34 tubes. Set the bias a little below average where I liked it to 33.1 ma. I'll let it burn in for a few hours. Can't believe it's done. 😄