ST-70 Power Transformer

moodyj2000 wrote:I am still dealing with parts and pieces from the lot of Dynaco I purchased.  The next piece is the power transformer.  The bottom cover has holes on the bottom and not on the side like I have seen in most PA060 transformers.  Anybody familiar with this?  I don't have a clear picture of the bottom but will take some more this evening.

I am thinking I need to verify this transformers functions.  Wire colors are fadded so its hard to determine which wire is what.  I've seen the spec's on another post on this site.

Below are the colors and layout of the original Dynaco PA-060 ST-70 power transformer and A-470 output transformers. If you take off the transformer covers, you may be able to find the actual wire colors. Try that and see if the wires on your transformers are the same colors as indicated on the transformer spec sheets. Note that the measurements shown in the diagrams are in inches.

Bob

PA-060 power transformer below



A-470 output transformer below

moodyj2000 wrote:Thanks Bob for the diagrams.  Yes, it definitely is not a PA060.  Just happen to come across a youtube post buy Uncle Doug, who I watch a lot since I am a newbie, and he addressed diagnossing unknow transformers.  The transformer he was using looked exactly like what I have.  It was a Baldwin Organ power transformer.  Did some more digging and wire color and everything are an exact match.  This came off of the chrome plated st-70 that I bought in this lot so somehow it was being used.  Found the following specs for it:
Red/red-yellow/Red: ~360-0-360V (for B+)
Yellow/yellow: ~6.8V (6.3V nominal for 12XX7 and 6X6 filaments)
Brown/brown: ~5.3V (5V nominal for rectifier filaments)
Green/green: ~14V (15V nominal for relays, etc.)

How could that have even been used?  This was for the unit that had the chassis punched out for a second rectifier tube.  

Main question now is can/should this be used for a stock ST-70 rebuild?

Steve Podski wrote:Hi Bob,
Do you have any fixes for a buzzing power transformer in a ST-70. No noise from speakers but when you   put your hand on the cover you feel it.

Yes .. Go to your local Lowes or Home Depot store and pick up some flat rubber washers that have a hole just big enough that an 8 X 32 screw will fit through the center hole. Place the washer between the bottom of the power transformer and the TOP of the chassis. Tighten the washers until they are firm but not over tight. If you still get some vibration out of the power transformer, try altering the amount of tension on the screws that hold the power transformer to the chassis. See link below from Home Depot. The photo at the link shows what they look like but these may not be the exact size you need ? Maybe bring an 8 X 32 screw with you and find some rubber washers that the screw will fit the opening in the washer. Photo and link below ..

Rubber anti vibration washers at Home Depot



Bob

Steve Podski wrote:Hi Bob,
Do you have any fixes for a buzzing power transformer in a ST-70. No noise from speakers but when you   put your hand on the cover you feel it.