Fisher Warwick - 1965

[Motorola minion]

I have downsizing to do on Fishers, having four complete and insides of two SS consoles!

Fortunately, I sold the 1967 Custom Electra 10 - all SS, after swapping in a Garrard AT6 to replace the Dual 1009, which lost its rubber in the spindle changer.

This Fisher Warwick is electrically the same as another Fisher Warwick. Both are model W-59, with a suffix unique to the cabinet. Both have a tubed tuner/preamp with MPX feeding a separate amplifier chassis. On this amp chassis is a 12AX7 and (2) 6HU8/ELL80 which drive interstage transformers that feed the FOUR (4) output transistors. Those transistors were "doubled up" on amplifiers rated for more power such as Ambassador's 59A (ratings on the Germanium transistors (NTE121/2N2148) are limited compared with silicon types such as NTE130/2N3055). Rework is possible to use silicon output transistors, because its not direct-coupled from drivers, instead from a small transformer that splits phase and matches impedance to drive the outputs.

I intend to keep the contemporary one and sell the provincial one. Both need restoration, which includes the Garrard type A changer in both consoles. This should not be too tough with all the spare parts I now have.

Ill have to get some pictures, I thought I had

[William]

Sorry, Dave, but no photos.

Bill

[Firedome]

One of them thar Warwicks that Dave has (in Eye-talian Provincial style, not the prettiest) was one that I found on CL being sold ($50?) by a local minister in Bingo. I picked it up and it ended up with Dave. By '65 Fisher cabinets left something to be desired: heavy, lots of particle board, weak legs, kinda ugly. No loss to sacrifice it that others may live, and glad it can serve to keep 'em going!

I'm surprised they had Germanium output xstrs. HHScott was smart, delayed a couple years, and went right to Silicon.

I also gave him my late Uncle's Type A, + Pickering cart, complete with original sales receipt from 1960? [my Uncle saved everything!} He'd bought it new to use with his tube McIntosh system (2 Mc-30s, Mc C-20, Mc MR55 tuner + M6 mpx that my cousin got and sold... $$$$) and 2 University Rebel V kit speakers he built that I now have. Again, at least the Garrard may be useful for parts or re-use hopefully.

[Motorola minion]

These two Fishers have one of the most interesting views from the rear. One obvious harbinger of the future you see on almost all the later consoles is enclosed (boxed) speakers using particleboard (not MDF) where plywood was normally used. The tube map is located below. There is no cabinet back cover, you can see it all.

The contemporary Warwick looks like a Futura and Ambassador, while the Italian provincial is walnut with a darker finish.

1965AmbassadorVIIContemporary (Warwick).jpg (152.16 KiB) Viewed 2330 times

[Firedome]

That's a true hybrid: all tube except the amplifier output stage.
Is it possible, or desirable, to replace Ge transistors with Si?
I know naught about SS stuff.

[electra225]

Are the transistors that bolt down the ones you call germanium? If so, I have some. I think they are NOS. I could look and give you the numbers I have if you have interest. Like Roger, my SS knowledge is at best basic.

[TC Chris]

I've read about germanium-to-silicon conversions. They are possible but require some re-engineering to get the voltages right for the new devices. It's a bit beyond my pay grade.

Chris Campbell

[hermitcrab]

Fishers are nice sets

[Motorola minion]

That's a true hybrid: all tube except the amplifier output stage.
Is it possible, or desirable, to replace Ge transistors with Si?
I know naught about SS stuff.

As Chris said, it can be done . I played with tubes initially but really learned ohms law, AC circuits and transistors first, in HS vo-tech. I struggled to get my Dynaco SCA-80 working thru 11th grade and had no success with direct-coupled silicon circuits, toughest of all but most desirable too. It was only after successfully repairing TVs (Philco and Zenith) using all Si transistors, I understood how transistors live and die. Integrated circuits were just a tiny step after that.

Two important differences between any and all transistors; polarity-NPN vs PNP and material-Silicon vs Germanium

Polarity requires swap of wiring to transistor sockets to reverse collector and emitter on all 4 output transistor sockets.
Material determines voltage drop across the P-N junctions, .5-.6 volts for silicon and .1-.2 volts for germanium.
Change in base-emitter current (like grid-cathode voltage in a tube) causes a much larger change in collector-emitter current (or plate to cathode voltage), the ratios of which determine gain.

Normally, an interstage driver transformer splits the phase to both outputs, resistor values control bias setpoint and WILL need to be changed (this be the hard part) to provide for the increased bias required for silicon.

The 2N3055 is NPN Si, aka NTE-130. These are easy to find unlike germanium transistors, nearly always PNP and require negative power supply. Silicon rules due to the superior switching speed, thermal stability and increased power handling "unleased" the real solid state revolution and opened the door for quality imported amps.

The 2N3055 bolts in and is socketed as E225 noted, TO-3 case like most transistors capable of high power. "Power tabs" are TO-220 case which also can attach a heat sink, often used in less expensive amps.

Shang066 has a YT video where he explains and demonstrates how to re-design an output stage to use silicon.

[Firedome]

Very interesting... wish I knew more of the theory behind SS circuit design but it's a bit heavy at my age. This week working on our final tool dispersal from his estate I found a little transistor checker my Uncle may have built from a kit, it has a switch for N-P-N and P-N-P selection, so assume it works for both. Will save if for your next visit Dave. Don't know what type transistors are used for output on my SS Magnavox R231 receiver, but it's around a 1972 so would guess they were using Is by then, it does sound excellent.

[Motorola minion]

I have had to make use of the parts left over from the 64 Ambassador A69IP and 67 Statesman S692, both in provincial cabinets loaded with particleboard, that went up in the Kutztown Swap bonfire.

The A69 has nearly the same amp as the W59, except it has doubled output transistors, for a higher power rating. This amp and the heavier A69's 12" speakers will go in my Danish Warwick W59, while this IP version will be sold as all original with just better speakers and output transistors. The original RCA35144 outputs seem tired.

I was able to replace the speakers with ones from the S692, which solved the buzzy fuzzy sound issue on that channel. The right woof was also replaced, then I tested the crossover caps (3 per side) ESR was good.

The tuner is excellent, as most all Fisher tube models excel in this category. Selectivity and sensitivity are comparable to Zenith. The tuning eye is nice and bright. This tuner and a Garrard A70 will sell this console.

The S692 used an all SS 31R chassis, which is a drop-in. Even before I scrapped this outrageously styled cabinet, trying to get the receiver to work right was hopeless. Not likely it was caps but failing transistors causing several issues.
The good thing was the 31R's four DTG110B output transistors which were an upgrade to the W59 amp 49A, higher voltage and power ratings, that best of the PNP-Ge technology, such as it is.

[Motorola minion]

Post note:
NTE 179 (DTG110) is the 'better output transistor that woke up the amp and they run cool, these are OEM on the more expensive SS Fisher amps/receivers.

OEM on the W59s amp was a tired set of NTE 121 (RCA 35144), which has lower ratings.

[hermitcrab]

there is a 1967 Fisher statesman in my area for only 50 bucks and has all the original paperwork with it ...looks to be in good shape ... I just think the cabinet was one of fishers ugliest designs with the center jutting out from the speakers ... IMO... are NTE179 any easier to find than the 121's?

[Motorola minion]

there is a 1967 Fisher statesman in my area for only 50 bucks and has all the original paperwork with it ...looks to be in good shape ... I just think the cabinet was one of fishers ugliest designs with the center jutting out from the speakers ... IMO... are NTE179 any easier to find than the 121's?

121s are more common, aka 2N2148 I have a 63 Sylvania hybrid tube-SS using them.

Electra225 has some 179s he wants to rehome, its the better one IMHO. Fisher used it as a DTG110E, who actually made it is in question though.

A $50 Fisher S692 is reasonable for a part out, since this IP Warwick needed speakers and transistors from one I sent to the bonfire. I got that one from habitat for $40 with a good Dual 1010 TT, but missing its R2R . The Statesman cabinet was outrageous and clumsy, getting any parts wet spells structural death.

I have enough in junk chassis to service the transistor-output consoles I was silly enough to bring home .

[Motorola minion]

The Fisher progress has been good, especially the amps with SS outputs. I have two good A49-T amps, three good tuner/preamps doorstop 690-A amp (fubar).

Fisher Warwicks I have are almost done. One has been converted to a 3-piece, as that IP cabinet sat at my antique booth too long and when I brought it home, breaking off two legs I had previously repaired while unloading it. That was that last straw - I cut both speaker enclosures off and removed all the cheap cabinetry in the middle. The amp speaker and TT will now occupy a small cabinet. It could sell that way because any clean Fisher chassis is just too pretty to hide in a cabinet, working on them is pretty easy due to a superior build quality and a well-designed chassis layout.

The other Warwick is a looker and needs to be sold. What I was considering, repairing the 690-A amp using power trans and output transistors from one of the functioning but lower-powered A49T amps, was not meant to be. That Ambassador had lemon written all over it when I broke the legs off just by moving it

Comparing both the Warwick A49T amps, some of HV PS caps were bad in one and LV PS caps open in the other one. Italian-made electrolytics were OK in one, bad in the other, so I changed all . Same parts, different fails due to long hours? storage environment? Another thing noticed about these amps was both had bias pots (to compensate for differences in non-matched PP output transistors) that were removed or disconnected with a thermal junction in their place. This was probably a post-production modification, adding a level of self-protection to the output transistors. As this component would increase in temp from surrounding environment, resistance increases to lower conduction current, sparing an output transistor from thermal runaway.

The 690-A, otherwise identical with exception of 4 more output transistors and 4 wirewound bias pots, had several reasons to fail. The power transformer HV secondary opened due to bad 100 mf - 200v doubler caps, one of the 2 diodes may have shorted as well. The HV supply powers all
tube stages. The LV PS was OK and none of the output transistors were shorted, no fuses blown. Anyway, only 5 of the 8 the transistors tested good.

There are a total of 16 PNP Ge (NTE-121) transistors and I needed to weed out the best ones. I determined the best one by sampling voltage drops across the emitter-base junction. Turns out, only 9 of 16 passed the test. Test criteria requires a DMM with a diode test function reading in VOLTS (not ohms):
1. Pull out all transistors, mark where they were first, in case unit has bias pots. Otherwise mixing up is not an issue.
2. put negative meter lead on base, positive on emitter, about 0.12 volts is good! (silicon is 0.6 volts) A steady beep and 0 volts drop is a shorted junction, no reading is an open junction.
3. reverse leads with neg on Emitter and pos on Base, there should be no less than 2.3 volts. If less, junction is failing. Ideal is infinite resistance and no measurable drop. Only the 9 good ones passed this test, most others were about 2.1 volts reversed, still almost the 10:1 ratio.
4. use only the transistors that test this way, never re-install a shorted or open one!

The Fisher-made speakers in Ambassador and Warwick are identical, only the extra 4 output transistors increase output power from 50 to 75 watts (assumed 20-30 wpc stereo). I believe the lower rated chassis is worth repairing while the 690A appears to have too many issues that will prevent it from being reliable. Nobody wants an SS console they sold to fail in field, because its probably the end.