Sylvania Exponent 4/40 Sound Issues
 

I have been working on this unit for a few weeks. The problem I am having is with the sound ouptut from the Garrard turntable. The sound is fuzzy and distorted--especially on vocals. Some album tracks sound better than others but even then the clarity is not there.
The unit has a brand new ceramic cartridge & needle. I have played a CD player and a tape deck through the AUX inputs and the sound is great, crystal clear. I plugged in my headphones and got the same great sound.
The turntable through the headphones sounds the same as the speakers-bad.
Any advice on where to start looking would be appreciated. Thanks.

Check tracking weight of the tonearm against published specs for whatever cartridge you're using.

Also if you're replacing the original ceramic or crystal cartridge with the same model in NOS it's possible that most of that make and model are uniformly failing from age.
Rubber parts break down with age as can the piezoelectric elements...If a certain cart was only made for 2-3 years and they've all past the expected life of the perishable parts of the internals, then finding a good one NOS or used becomes similar to playing the lottery.
I often replace bad original ceramic/crystal carts with the ones the crosley reproduction players use because I'd rather spend $2 once and have it work than $40 2-10 times till I find a correct NOS part that isn't DOA from old age.

Thanks for the info. I will check it out.

Shango has this up.

https://www.youtube.com/watch?v=e0DkojD6NBk&t=576s

I would check both cartridges specs. They vary wildly on output.
Odds are this one wants a low output cart. There is an Astatic
catologue on the net & surprisingly readable !
And yes NOS carts are going bad on the shelf. And other things
you wouldnt expect.

73 Zeno:smoke:
LFOD !

Is there a chance that this unit may take a magnetic cartridge instead of the ceramic I installed?

Thanks,

Unlikely for direct connection. Most ceramics are more than 10x the output voltage of a magnetic cart...So if you convert to magnetic you'll probably need to add a preamp.

Ok, thanks.

Good possibility the original was magnetic based on the results you are getting. Did it not have a cartridge when you acquired it? Do you have a resistor substitute box? If so hook it between the output of one channel of the cartridge and ground. Start high and start lowering the value and see what happens. It may attenuate the output, low enough that you will be able to determine that you need a magnetic cartridge instead of the ceramic you have installed.

Yes, the cartridge/needle was a ceramic setup when I got it. Thinking that this was the problem for the distorted sound I purchased a new ceramic combo and got the same results.
This is a early model for the Exponent (1965?). The model number is 4/40-0. The Photofacts show a Astatic ceramic replacement part#. I seen other post that magnetic came along in 1966/67 with model 4/40-2.

If the astatic Sam's for the 4/40-0 mentions is a ceramic look up it's data sheet and compare it's output voltage spec to the spec for the new cart you put in....If the new cart has a higher output voltage it could be overdriving the amp into distortion.

Will do, thanks.

Tom,
You might have a possible answer there. The original Astatic 181D cart listed in the Sam's has an output of .11v. The Pfanstiehl P-132D that was recommended has a replacement and was installed lists a .40v output. Would that difference be large enough to overdrive the amp?

Yeah nearly 4X input could definitely cause an overload. I'd be tempted to put a 50k pot or voltage divider circuit on the cartridge input to the amp for one channel and see if reducing cartridge output by %75 makes a difference in sound quality...If it does you've proved over drive and get to choose between finding a different cart that is a closer match or modifying it to scale down the voltage.

Thanks for the quick reply. Not sure which way to go for now. I did find a direct replacement cart. EV-5562D which has the .11v output. I'll post the results once I'm done.

Tried the 50K pot (left channel) and got the same result no matter where I set the pot. Should I look at getting the low output cart or is there something else to look at.
Thanks.

If you wired the pot correctly, you should have been able to adjust the signal level all the way from maximum to zero. Is that the result you got?
Was the distortion there even at low level?

L-attenuator using potiometer

Cartridge connects to Vin(1) and ground (3). Amplifier connects to wiper (2) and ground (3)


https://www.electronicshub.org/wp-co...entiometer.jpg

If you did it the way oldtvnut described and there is still distortion the next thing I'd try is connecting the cartridge to a different amp and checking for distortion. I'd look for a tube based device as those usually expect a ceramic cartridge on their phono input.
If distortion is still present on another amp I'd say it's the cartridge and get another one. If the distortion is gone with the same cart feeding a different amp, then the amp in the Sylvania is suspect.

Ironically I could have bought a rough one of these Sylvanias sans speakers yesterday for a buck in the WARCI swapmeet donation auction... I've got enough phonos and too little space so I passed.

Guy--thanks for the quick replies. Yes, per your diagram the pot was wired correctly. The pot did the range from low to high and at all levels the distortion was the same.
Tom--I'll have to ask around for an amp that takes a ceramic input. I currently have nothing that will do that.

I tried something off the cuff and was surprised by the reults. I ran the phono cable from the turntable to my ATUS AM150 mixer (magnetic phono input). Took the mixer output cables and plugged it into the AUX inputs on the Exponent. It sounded great, along with the bass and treble--no distortion. I then put the cable from the turntable straight to the AUX input on the Exponent. No distortion, but bass and treble was fair. What are your thoughts. I posted videos on YouTube with the distorted sound from the new cart and running with all Exponent internal cables. The second video shows the mixer hookup and the non-distorted sound. Y/Tube links:

https://youtu.be/_51NLbt21ho

https://youtu.be/6U6iTv3F-O4

Thanks.

So, the only common thing about the distorted case is going through the preamp?
Are both Left and right distorted? Or could one side of the preamp be defective?

https://live.staticflickr.com/65535/...02e2111a_h.jpg

Looks like the 25 volt supply is used by the right and left preamp stages and nothing else... is it ok? :scratch2:

jr

Yes, distortion is on both channels. I have not pulled the electronics out yet. Would the mixer test confirm that the cartridge/needle is good and the issue could be in the amp?

Seems to be leading towards that, especially if it was only one side.
Anyway, the usual suspects - power supply, electrolytics (the 1 microfarads), paper caps, then resistors.

I would start by checking the 25 volt supply, then check all voltages in the preamps. If 25 volts bad, fix it first. Then if internal voltages bad, check the 1 microfarad caps, then...

Checked 25 volt supply--it tested good.

I'd suspect caps, K1 and K4, the discrete resistors, and the preamp transistors in that order.

Bypassing the preamp with that external mixer pretty much confirms the preamp is at fault.

Thanks Tom--I will check those out.

PHONO pre amp is source trouble. ( X1 & X6 )
Try C3 & C8.
Check the 25V line. There should be a lytic cap there, change it.
Without signal check the voltages on X1 & X6 be sure they are very close.
If one is leaky it could effect the "good" channel & make both bad.
Used to happen to cheapo stereos in the 70's.
Be nice if you could post schematic of power supply area also.

Zeno:smoke:

Exponent
 

Zeno, I will check those out. I have attached a few Photofact sheets which cover this unit. Thanks.

Guys problem solved. Thanks to Electronic M & Zeno for their early guidance toward the cartridge. I changed out the current Pfanstiehl P-132D that put out .4/.5v. I installed a new Astatic 157 cart/needle from V-M (Gary was very helpful also). The 157 cart puts out .1V. Zeno's early remark of "this one wants a low output cart" stuck with me and so the change was done. Also, I really did not want to go digging around in the amp. Thanks to all of you for the comments. Everyone was most helpful.