JF Antique Radio Repair / Tube Amplifier Repair / Tube Equipment Repair
TUBE AMPLIFIER REPAIR
I have been repairing old and new tube amplifiers for the past 30 years. I have repaired many makes and models, including:
Dynaco's Dynakit ST-70
Fisher 400C, X100-B, 510-ST, 30-A
Harmon Kardon (HK) A500
Heathkit EA-3, W4AM, Stereo Amp
Knight KN-330 (Tuner/amp)
RCA MI-12224 (Early PA amplifier)
REPAIR VS RESTORATION
I repair equipment and do not perform restoration.
Restoration involves placing new parts within the shells of the old parts, or placing new parts inside of moulds of old parts that are painted to look like the old parts.
Repair involves installing new parts under the chassis. All exposed parts on top of the chassis stay in place (are not removed).
Defective components in old and new amplifiers shall be replaced.
For older amplifiers: all Filter, Bypass and Paper capacitors will be replaced; all Coupling capacitors connected to B+ voltage will be replaced. Tone and Coupling caps not connected to B+ are not replaced unless defective.
Quality of sound varies on the type of Coupling capacitor employed. Coupling capacitors vary in price from $2 up to $100 each. It depends on what sound the customer wants to use for their amplifier. Recommendations
will be made as to which type capacitor is best suited for a given amplifier.
For new and old amplifiers, all tubes will be tested for emissions and leakage (shorts) on a Triplett model 3444-A tube tester. Bad tubes shall be replaced with a manufacture specified by the customer. Recommendations will be made as to which
tube manufacturer is best suited for a given amplifier. I usually inform the customer which tube(s) is(are) bad and let them order after recommendation and have them shipped to me. This saves on repair cost.
Amplifier circuit modification to improve sound quality will be considered on a case by case basis, per customer request. Modification may adversly impact operation, so repair cannot be guaranteed. I will not install
soild state components in a tube amplifier.
TUNERS MANUFACTURED AFTER 1950
I generally do not repair tuners manufactured after 1950.
Tube tuners manufactured after 1950 have inferior IF (Intermediate Frequency) transformers (compared with IF transformers used in earlier radios). These transformers contain capacitors made of silver film on a mica substrate.
The silver is exposed to the elements, causing corrosion, and results in Silver Mica Disease. When Silver Mica Disease is present, tuners exhibit cracking sounds like lightning noise transmitted through the speakers.
I do not rebuild IF transformers (replacing silver substrate capacitor with a mica capacitor), therefore I generally do not repair these tuners.
If a scratchy noise is heard when tubes are wiggled, turn unit off, remove offending tube, spray Deoxit Contact Cleaner (red can) into the tube socket, reinsert tube, turn unit back, wiggle tube until noise is gone.
If unit produces audio hum with volume up, unit may need to be grounded. Connect a ground wire from center screw of an outlet cover to a chassis screw on the unit.
Pease contact me if you would like to learn how to repair amplifiers. I do not charge for this.