Description

Unloading a few more of my Magnavox tube amps. This is roughly my 28th year working with Magnavox amps. Letting go of a few really nice specimens, check my other listings if your looking for more or less power, SE or PP topology, etc. The pics tell the story, a VERY GOOD specimen needing some electrical restoration. It will need new capacitors, period. MOJO is not secretly contained in realy old capacitors, but.... loss of good working tubes is. Leave the caps and pay down the line in failed tubes and maybe transformer loss. Only a fool will leave the caps as is. This is of course a push pull design giving 14 watts per channel. I am on the fence as which PP chassis sounds best from Magnavox- I am an OCTAL guy so the 6V6 chassis are my deal. The 6BQ5 is known to have superior tone in most applications and a touch more power available. No restoration efforts have been made except to scrub some YUCK off the front of the chassis near the RCA inputs. Else, It was wiped with a damp cloth before pics. You will need to add a power switch to the chassis, there are plenty of pre-punched holes for mounting one. As well, you should remove the "death cap" which is in the AC line circuit. Also add a fuse holder in another pre-punched hole and preserve the amp for the future. I suggest replacement of the OE power cord with something less likely to embrittle and flake offering an opportunity to short and burn. Lastly, each resistor should be tested for correct value to ensure bias is both accurate and stable and gain is on par with the design spec. These are typical and sundry changes made to ALL aging tube power amplifiers to ensure a future long life of both tubes and transformers. Sockets are super tight and clean. Tube compliment and condition, as tested on a B&K 707. All tubes have sharpie marks that can be removed indicating the test results, removed easily with a cotton swab and rubbing alcohol. (2) 6EU7, original to chassis, 75/75 and 77/77 where 100 is a new tube. (4) 6BQ5, original to chassis, 83, 83, 83, 86 where 100 is a new tube. (1) 5U4GB, appears may be a replacement as it is Raytheon Branded 81/84 where 100 is a new tube. Typically Maggie OE tubes are ALL branded Magnavox. The matching of the 6BQ5 is well inside a new quad match of current production. Getter is just superb on the quad. The rectifier is typical spread on plates and very well balanced. Transformer condition: Output primaries measure (136 and 153) ohms (135 and 155) ohms. Transformer wind is very close between channels! Output secondaries are about 0.3 ohm (corrected for leads) Power trans - no open windings including the aux filament/pilot lamp winding. There is no doubt the transformers are healthy. I usually offer some suggestions for modifications to improve (my ears say so at least). You can bump the second filter cap section 10-20uF safely as the series filter choke will limit surge current values. As well the amp alone (no tuner chassis leaching current) is well beneath the capability of a 5U4GB, there is more recitifier headroom to utilize. Exchange all plate and screen resistors for those with lower noise characteristic. Metal films are nice and quiet and will lower the noise floor substantially. Amp currently has Allen Bradley carbon comp. Choice of a premium coupling capacitor will make another substantial difference. An Auricap is difficult to improve on for resolution improvement. Any resistor in the power supply distribution/B+ rail would be well to have a metal film replacement. Again simply to lower noise floor as best possible. You may rather perfer a warm FUZZY tone, that echoes 1940..... leave the AB resistors and run a simple film cap for coupling and call it good. Additionally the Magnavox PP chassis all are served well with a simple redesign. Substitution of a 12AX7 and 12AU7 for the two driver tubes, using them as a cascade. 1/2 12AX7 gain stage, direct coupled to 1/2 12AU7 in split load phase inverter mode, cap coupled to the power tube pair, biased at your preferred operating point is exceptional. As it is the 6EU7 send a highly unbalanced signal to the power tubes and driver phase balance is required for lowest distortion. A split load phae inverter goes a long wasy, cheaply and cleanly, toward providing good balance. The direct coupled gain stage eliminates a coupling cap which is just a bother and another pole to calc for roll offs. What you end up with a a less rare (ish) small signal tube (12AX7) that is highly rollable for your desired tone, etc..... feeding a NEUTRAL highly rollable, low cost 12AU7 which will survive much longer at modest currents. It is a win/win. Lastly bias the power tube pairs separately for Petes sake. Currently the amp runs a single sand cast resistor and bypass cap. Make it TWO resistors, TWO bypass caps and make the Left and Right channels as separated as possible. Very easy, cheap mods that can be done in a few evenings after work, etc. Suggest 12AX7 at 220k plate, 12AU7 at 22-47k each plate/cathode and calc the bias and plate voltages accordingly for direct coupling. I have not powered this amp since retrieval. It is sold as is with no warranty expressed or implied. It is listed as NOT WORKING as it doesnt work, I have not plugged it in therefore it is for parts and for you to restore----I am not restoring it for you. Shipping is FREE CONUS only, AK, HI are extra and will be quoted. I will ship by carrier I choose for best pricing and that is typically Fedex. I WORK, this is not my job here on Ebay. I travel for work and if you close this or any other auction and I am out of state, you will need to be patient for me to get the amplifier shipped out. Your patience will be rewarded, I am sure. If your in haste, dont bid, please! I never travel longer than 4 days and promptly process the day after I get back to Tennessee. See my feedback for confidence. Rare is it that folks wait longer than 3 days per Ebay rules due to my work, but of course it has happened in the past. Ask questions before you click bid or buy! I will answer them all and quickly. I will not ship Internationally, please do not ask.