HI all, Does anyone have the color codes for leads on a R145 AMI amplifier power transformer and resistance readings for the windings? I've found a transformer with very faded leads and may have to identify them with and ohm meter. Thanks, Dean
On 9/10/25 14:47, Dean Carriveau via Jukebox-list wrote:
HI all, Does anyone have the color codes for leads on a R145 AMI amplifier power transformer and resistance readings for the windings? I've found a transformer with very faded leads and may have to identify them with and ohm meter.
Black = 120VAC common Black/yellow = 117VAC in Black/red =125VAC in (Above from schematic)
Below is the standard power transformer color code:
Red = High voltage out Red/yellow = High voltage center tap Green = 6.3V filament Yellow = 5V filament
The filament wires will be higher gauge than the primary and HV secondary and very low resistance. Primary will be higher resistance and HV secondary (with center tap) highest resistance. Also check between windings and to case to ensure that you don't have any shorts.
Final test would be to separate the wires so nothing can short. Connect 120VAC to black and black/red. Measure the voltages on the other wires. Be very careful, high voltages involved.
Jay, Thanks for that information. I appreciate it. I've got the schematic and like you was only able to I.D. the 120VAC for sure. The wire insulation is so dirty or faded it's really hard to tell what color most of the other leads should be. I'll get my meter and check voltages on the other pairs and hopefully not end up doing an involuntary dance! Dean On Thursday, September 11, 2025 at 11:44:37 AM PDT, Jay Hennigan via Jukebox-list jukebox-list@lists.netlojix.com wrote:
On 9/10/25 14:47, Dean Carriveau via Jukebox-list wrote:
HI all, Does anyone have the color codes for leads on a R145 AMI amplifier power transformer and resistance readings for the windings? I've found a transformer with very faded leads and may have to identify them with and ohm meter.
Black = 120VAC common Black/yellow = 117VAC in Black/red =125VAC in (Above from schematic)
Below is the standard power transformer color code:
Red = High voltage out Red/yellow = High voltage center tap Green = 6.3V filament Yellow = 5V filament
The filament wires will be higher gauge than the primary and HV secondary and very low resistance. Primary will be higher resistance and HV secondary (with center tap) highest resistance. Also check between windings and to case to ensure that you don't have any shorts.
Final test would be to separate the wires so nothing can short. Connect 120VAC to black and black/red. Measure the voltages on the other wires. Be very careful, high voltages involved.
On 9/11/25 12:51, Dean Carriveau via Jukebox-list wrote:
Jay, Thanks for that information. I appreciate it. I've got the schematic and like you was only able to I.D. the 120VAC for sure. The wire insulation is so dirty or faded it's really hard to tell what color most of the other leads should be. I'll get my meter and check voltages on the other pairs and hopefully not end up doing an involuntary dance!
If you have a 12 volt transformer (a real AC transformer, not a DC wall-wart) you can feed the primary from that and scale the secondary voltages to 10% of nominal which will be safer. Variac will work as well, same idea.
Thanks Jay, I printed that out for future reference.
On 9/11/2025 2:43 PM, Jay Hennigan via Jukebox-list wrote:
On 9/10/25 14:47, Dean Carriveau via Jukebox-list wrote:
HI all, Does anyone have the color codes for leads on a R145 AMI amplifier power transformer and resistance readings for the windings? I've found a transformer with very faded leads and may have to identify them with and ohm meter.
Black = 120VAC common Black/yellow = 117VAC in Black/red =125VAC in (Above from schematic)
Below is the standard power transformer color code:
Red = High voltage out Red/yellow = High voltage center tap Green = 6.3V filament Yellow = 5V filament
The filament wires will be higher gauge than the primary and HV secondary and very low resistance. Primary will be higher resistance and HV secondary (with center tap) highest resistance. Also check between windings and to case to ensure that you don't have any shorts.
Final test would be to separate the wires so nothing can short. Connect 120VAC to black and black/red. Measure the voltages on the other wires. Be very careful, high voltages involved.
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