OFF - FOR SALE: Heathkit W-5M Monoblock Pair
Item #649394750Info: Heathkit W-5M Monoblock Pair
||Cash, Money Order, Interac/EMT
||6 - Fair (?)
Nov 23, 17 6:13pm (PST)
Edited: Dec 31, 17 4:26pm
North Vancouver, BC
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Offered for sale are a restored pair of Heathkit model W-5M, 25 Watt mono amplifiers plus cages.
Owning and rebuilding these has given me great pleassure but it is time to find them a new home and clear some space for the next project.
The restoration of the amps was done following the original circuit design with a minor modification to better stabilize the high frequency response. Some additional upgrades as follows were made to improve looks, functionality and protection:
1) The two multisection capacitors (silver cans) on top of the chassis were removed and replaced with individual capacitors below the chassis to improve looks and provide better cooling flow around the power tubes.
2) A double pole on/off slider switch was installed in place of the top rear chassis receptacle (the original design had no power switch).
3) An electronic time delay reduced voltage start up circuit was designed and installed to simulate the thermal mechanical "surgistor" supplied in some of the later W-5M models (presumably in an effort to soften the startup impact on the power transformers which were known to have reliability issues).
Values of components used in the restoration were individually checked, and matched where needed. Power output, gain and frequency & square wave performance of the amps were checked on completion of the work. Since the restoration, the amps have had roughly 25-50 hours of playing time.
Both amplifiers have the same (factory supplied) Altec Lansing Peerless model 16309 output transformers (some W-5M's were supplied with a 16458 model output transformer).
All tubes are supplied with the amplifier. These consist of two 12AU7's (driver and phase converter), one 5R4GY rectifier and two 6L6WGC output tubes. The rectifier and 12AU7's are old stock American made and the output tubes are a new matched set of Russian 6L6WGC which have about 12 hours of operation needed for breakin. (Operation of the Bias currents and balance of the output tubes are noted to be rock solid.)
Due to the approximate 60 years age of the power and output transformers, sale of the amps is on an "as is" basis with no warranty or guarantee.
As with all tube amps of this age, it is best from a reliabilty (and I have found better sound) standpoint to supply them at 115 VAC versus the typical 120-125 found in most homes today. (A reasonable cost approach to this is to use a single small 115 / 6.3 Volt 4 amp transformer such as a Hammond 166N6 wired as an autotransformer to power both amps at 95% line voltage.)
Audition of the amps is available to serious buyers. Local sale is preferred. Shipping is extra to the asking price and would require two separate boxes at approximately 30 lb each.
Included are: The factory cages (though hardly noticeable, one has a wrinkle finish, the other does not); A coil bound reprint of the 33 page manual with schematic diagram updatde to cover the modifications, vacuum tubes as described above with shielding sleeves for the small tubes.
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