Author Topic: 1959 Zenith SFD2505  (Read 2084 times)

Motorola Minion

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1959 Zenith SFD2505
« on: September 28, 2015, 08:21:14 AM »
I saw this on locally on craigslist and by the time I contacted the seller, he said it had been dropped off at Goodwill, even closer to my place.
Checking the store, there is a "bargain room" with bins of everything and very used furniture, and there it sat with a $15 tag on it :)

I first noticed an all-too-common BSR record changer and it was just dropped in there, not plugged in. Assuming there was a Cobramatic that was pulled out at some point, there was likely ntion of bring this unit to life. :(

I then realized I had a spare 1970 Zenith 2g record changer, made by Voice of Music and this was a STEREO single ended 6BQ5/EL84 tube amplifier with two 12AX7 preamp-1st AF tubes :D

I worked for about 2 hours disassembling, cleaning and adjusting the gummed-up changer last night before realizing the cartridge had a dead channel. The stylus I had replaced as S.O.P. and since I see these often, I had a spare. The changer operates correctly on 10 and 12 inch records, so I'm ordering a cartridge today. While I am waiting for it, the AMP needs the usual re-capping. At this point, I just hope the power and output transfomers are OK.

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Dave

vintage cltr

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Re: 1959 Zenith SFD2505
« Reply #1 on: September 28, 2015, 08:41:28 AM »
nice unit. great story.
Loud and Vintage.... any questions?

Larry H

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Re: 1959 Zenith SFD2505
« Reply #2 on: September 28, 2015, 11:10:06 AM »
Cabinet looks like brand new.  Not even yellowed looking.  Great deal for the price.
--Larry

Pat L

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Re: 1959 Zenith SFD2505
« Reply #3 on: September 28, 2015, 11:12:46 AM »
I'm guessing it's from 1959?

Harbourmaster

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Re: 1959 Zenith SFD2505
« Reply #4 on: September 28, 2015, 01:52:55 PM »
Nice looking record player.  I believe that Zenith refers to this color as "Bisque".
-- Aloha, Ken

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Motorola Minion

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Re: 1959 Zenith SFD2505
« Reply #5 on: October 06, 2015, 11:10:04 AM »
I just finished recapping the chassis. It took 1.5 hours and was like performing surgery with the way the caps are buried, kinda like a Philco ::)

Unfortunately, the original stereo Cobra changer is long gone. But I do have an untested 1958 Zenith (Mono 6V6 p-p w/AM-FM) console HF1284 that has one, so Ill have that experience in mono.

The newer changer is operating well with a new part#142-167 OEM-style cart and needle thanks to Gary at V of M. Oh, and it needed the idler pulley rebuilt, of course but I can't wait to hear this play :)
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Dave

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Re: 1959 Zenith SFD2505
« Reply #6 on: October 06, 2015, 03:12:04 PM »
After reading Pat's experience with weak tubes, I hope this unit has low-hours. All tubes are original but at least its single-ended.
Have $65 plus caps invested so far and I hate to buy tubes :-[    since I have so many untested used and precious few NOS 6BQ5s and 12AX7s   
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Dave

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Re: 1959 Zenith SFD2505
« Reply #7 on: October 07, 2015, 03:16:02 PM »
After the recap, I plugged the 5Y3 rectifier tube in and powered it up to see if the power trans was OK. After measuring over 500 volts DC, I realized there was no load with the other tubes out of socket. After plugging them in and adjusting line to 120 on the variac, it was 372 on the 5Y3 cathode.

Of course I did not have the Sams, so I looked harder for the "gold" info and got lucky for a change
Zenith publication HF-4 for all 1960 High Fidelity and Stereophonic models (I have 1960-64 if anyone needs scans) I wanted to measure all the voltages on the tubes before "going live" and pushing sound through it.

I measured 12 volts on the 6BQ5 cathodes and zero on the grid, about right on for proper bias. The voltages on the 12AU7 AF driver was close on both triodes. When I got to the 12AX7 pre-amp tube, things were not right and note even on both channels either. After a power down and cap discharge, both 100K plate resistors were waaay off, @ 160K and 180K, so i replaced them with the best 10% pair in the drawer, 104K and 107K.
After replacement, voltages were 150-152 on the pre-amp tube plates.
Then I noticed the pickup wires lacked RCA plugs. I found a cable and soldered it onto the input plug, adding a stereo mini in parallel. I do this when I might sell a set because many play ipods and cellphones through console units as opposed to only playing records.

One thing lacking on this console is a pilot light ???, so I will connect an "under hood" lamp to the changer motor like my Motorola has.

After all this unplanned work, it was late and I did not want to risking waking the house by testing this unit the right way.
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Dave

Motorola Minion

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Re: 1959 Zenith SFD2505
« Reply #8 on: October 08, 2015, 12:07:39 PM »
Is anyone familiar with the items on the tone control shafts. There are no windows or backlighting on this model.
The second picture shows the replacement mylar caps stuck on their predecessors for convenience.

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Dave

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Re: 1959 Zenith SFD2505
« Reply #9 on: October 08, 2015, 12:26:10 PM »
Without actually having the piece in my hands I would guess that they are stops of some sort, or that the shafts are multi piece affairs and these clamps hold them together.
-- Aloha, Ken

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Motorola Minion

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Re: 1959 Zenith SFD2505
« Reply #10 on: October 09, 2015, 10:28:47 AM »
The shafts are actually the balance and loudness. they spin together so maybe I need to loosen up the clamps and lubricate them.

After installing the chassis and changer, I played a record and there was ample loudness, from one speaker.
I noticed one of the external speaker "bypass" plugs was missing and made a jumper.

Depsite needing a tracking force and anti-skate adjustment, what I heard was great!

I also need to fix some blemishes in the blond photofinish and need some help finding proper touch up paint.
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Dave

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Re: 1959 Zenith SFD2505
« Reply #11 on: October 13, 2015, 12:50:14 PM »
The clamps are adjusted so that both pots will turn when just the outer knob is turned, but loose enough if the inner shaft needs to be "matched" to the outer.
These pots are separate left and right volume controls, not a separate balance and loudness, which is what the labeling implies.
After "bypassing" the speaker plugs and making adjustments to the 2g record changer, the sound is sweet ;), even on 10" 33.3 rpm records, which require you to spin the two head stylus to the sapphire "78" selection.

There are two issues with the replacement cartridge;

1- when the knob which spins the stylus points to "78" on the tone-arm head shell, it puts the "LP" stylus on. Since Id rather not pull the styli off the arbor to reverse them or mangle the tiny shaft to put the knob on right, the head shell needs to be re-labeled.

2 - The sound practically goes away when I pull up the bass control knob to go from stereo to mono, which joins the two inputs from changer to amp. I suspect the cart has the polarity backwards between channels. I suppose this can be solved by reversing the tone arm leads from one channel under the platter. :-\
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Dave

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Re: 1959 Zenith SFD2505
« Reply #12 on: October 22, 2015, 09:19:17 AM »
After playing newer stereo records, I noticed the usual difference switching from Mono to Stereo.
I also had an issue with a low level hiss (shot noise) that began shortly after warm-up.
I replaced the Zenith-branded Amperex 12AX7 with a British 12AX7 and now that issue is cleared up. :D

After adding a light, its ready for a new home.

As much as Blonde or Heywood-Wakefield furniture is attractive to some, late '40s Magnavox Windsor Imperial and Berkeley I have are better suited to our 150 YO house.
Those two will take a bit longer to restore.
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Dave