HOFFMAN TRANSFORMER WIRE DIAGRAMS AND SPECIFICATIONS
Note : All of these transformers were discontinued a long time ago. |
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HOFFMAN OUTPUT TRANSFORMERS |
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| Part Numbers | DESCRIPTION | 
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| H30W0 | 30 Watt Output Transformer | |
| H50W0 | 50 Watt Output Transformer | |
| H100W0 | 100 Watt Output Transformer | |
| HOFFMAN OUTPUT TRANSFORMER SPECS | ||||
| OUTPUT SPEC'S | H30WO | H50WO | H100WO | H50MC choke |
| MOUNTING CENTERS | 2" X 2 1/4" | 2 1/2" X 3" | 2 1/2" X 3" | 2 3/8" |
| WIDTH | 2 1/2" | 3 1/8" | 3 1/8" | 1 5/8" |
| DEPTH | 3 1/8" | 4 1/8" | 4 1/8" | 2" |
| HEIGHT | 3 1/8" | 3 7/8" | 3 7/8" | 1 5/8" |
| WEIGHT | 3 LBS | 6 1/2 LBS | 6 1/2 LBS | 10 oz. |
| MAX RATING ANY TAP | 50 WATTS | 75 WATTS | 150 WATTS | 50 MA |
| PRIMARY IMPEDANCE | 4000 OHMS | 4400 OHMS | 2200 OHMS | 8 Henry |
CONNECTING OUTPUT TRANSFORMERS.
Connect the black and white leads to the plates (Usually Pin 3).
If the amp squeals from POSITIVE feedback, reverse the black and white leads so that the amp receives NEGATIVE feedback.
On most amps the black lead usually goes to the power tube closest to the rectifier tube or power transformer.
Power transformers
Note: All my power transformers used a bridge rectifier.
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| HOFFMAN POWER TRANSFORMER SPECS | ||||
| POWER SPEC'S | H3APA | H30WP | H50WP | H100WP |
| MOUNTING CENTERS | 3 1/8" | 2 1/2" X 2 7/8" | 3" X 3 5/8" | 2 1/2" X 3" |
| WIDTH | 2 1/2" | 3 1/8" | 3 3/4" | 3 3/4" |
| DEPTH | 2 3/4" | 4 1/8" | 4 5/8" | 4 5/8" |
| HEIGHT | 2 1/4" | 3 7/8" | 4 5/8" | 4 5/8" |
| WEIGHT | 2 LBS | 6 1/2 LBS | 10 1/2 LBS | 10 1/2 LBS |
| B+ WINDING AC | 225 VAC | 282.8 VAC | 343.5 VAC | 343.5 VAC |
| B+ RECTIFIED DC | 290 VDC | 360 VDC | 460 VDC | 460 VDC |
| B+ WINDING CURRENT | 100 MA | .5 AMP MAX | .5 AMP MAX | .7 AMP MAX |
| BIAS WINDING AC | NONE | 100 VAC | 100 VAC | 100 VAC |
| HEATER WINDING | 6.3 VAC | 6.3 VAC | 6.3 VAC | 6.3 VAC |
| HEATER CURRENT | 3 AMPS MAX | 6 AMPS MAX | 6 AMPS MAX | 8 AMPS MAX |
NOTE: ALL B+ WINDINGS USE A BRIDGE RECTIFIER .
THE FORMULA IS AC VOLTS X 1.4 = DC VOLTS UNLOADED.
EXAMPLE 282.8 VAC X 1.4 = 395.92 VDC.
ONCE THE AMP IS UP AND RUNNING THE B+ WILL COME DOWN.
EXPECT AROUND 350 TO 360 VDC UNDER LOAD.
NOTE: This is just a rough estimate, this formula is not exact.
There is no way to get an exact figure.
The final B+ voltage depends on many other factors in the amp.
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HOFFMAN POWER TRANSFORMER HOOK UP CHART |
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| LINE | CONNECT | CONNECT | DO NOT USE | |
| 100 VAC | 1 & 4 - 2 & 5 | 1 & 4 | 2 & 5 | 3 & 6 * Note |
| 120 VAC | 1 & 4 - 3 & 6 | 1 & 4 | 3 & 6 | 2 & 5 *Note |
| 220 VAC | 1 & 5 | 3 & 4 | 2 & 6 * Note | |
| 240 VAC | 1 & 6 | 3 & 4 | 2 & 5 * Note | |
| * Note: do not twist these leads together, keep them separate. Heat shrink each end so they do not touch anything. | ||||
| EXAMPLE : For 120 VAC use * Twist together leads 1 and 4. * Twist together leads 3 and 6. * Use leads 1 & 4 and 3 & 6 for connection to the power cord. * Do not use leads 2 and 5. Do not twist leads 2 and 5 together. Heat shrink them separately and tuck them out of the way. |
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