Dual 1237 not delivering the best audio

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Tazzybehr
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Dual 1237 not delivering the best audio

Post by Tazzybehr » 31 Mar 2019 22:32

Hi.

I bought a "new to me" Dual 1237 turntable. When I hooked it up to my new to me refurbed amp, I noticed my records all were missing the sharp high instruments, and things didn't sound as crisp and clear as my old system sounded. Horns were barely audible, and strings, even less. So, me being me, I took the amp out to be repaired. When the tech hooked it up to his speakers and turntable, it sounded pretty damned good. He even hooked up a comparable receiver, they both sounded decent. Knowing that my speakers weren't the problem, I am now looking at the turntable. Now, I've never heard of a magnetic cartridge going bad, but who am I to assume? I do know from reading there is a capacitor that can go bad in the unit, and causes popping noises. I can't say I've heard that symptom, but to be sure, I've ordered a new one on Ebay. So...I guess I'm asking, does anyone know if there is other circuitry built into this turntable? If so; would simply replacing the caps fix my audio issue?

Thanks for your time. Dave. :D
Last edited by Tazzybehr on 31 Mar 2019 23:23, edited 1 time in total.

tlscapital
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Re: Dual 1237 not delivering the best audio

Post by tlscapital » 31 Mar 2019 22:50

What sort of connectors does the tonearm cables have ? Din, RCA... Likely if corroded or worn it/they could be replaced. This is a classic replacement that will instantly in many cases bring back the good sound in full.

If ever, a recabling (1 mete max, low capacitance and shielded) can be welcome as well. How about the inner tonearm wiring ? Is it still looking good and in place ? And the what about the cartridge and stylus, what are they ?

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Re: Dual 1237 not delivering the best audio

Post by musicmn » 31 Mar 2019 23:00

Hi Dave, the caps used in this turntable are only for the motor. And when they go bad you can here a popping noise from your speakers when the turntable turns off. Another issue if the caps are bad would be the motor jogging back and forth or the motor spinning backward on start up. There is a mute switch in line with the tonearm wires and rca cables. The contacts do get very tarnished over the years and this might account for the muffled sound. But my guess would be either a bad stylus or a very dirty stylus. It could even be a bad cartridge but usually they just go bad. Another place that needs cleaning is a small circuit board under the tonearm. Remove the cartridge sled and look up under the tonearm end. You will see the circuit board the contacts are always black from tarnish. Use a pencil eraser to clean them up until they are shiny. You should also clean the end of the pins on the cartridge sled and while your at it check the tags on the end of the cartridge sled wires. If those are black from tarnish use a solution of backing soda and water and a old tooth brush to clean off the tarnish. Finally check the rca cable ends if those are the original black and white ends they loose there plating over the years and usually need replacing at this time. I hope something here helps.

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Re: Dual 1237 not delivering the best audio

Post by Tazzybehr » 31 Mar 2019 23:12

musicmn wrote:
31 Mar 2019 23:00
Hi Dave, the caps used in this turntable are only for the motor. And when they go bad you can here a popping noise from your speakers when the turntable turns off. Another issue if the caps are bad would be the motor jogging back and forth or the motor spinning backward on start up. There is a mute switch in line with the tonearm wires and rca cables. The contacts do get very tarnished over the years and this might account for the muffled sound. But my guess would be either a bad stylus or a very dirty stylus. It could even be a bad cartridge but usually they just go bad. Another place that needs cleaning is a small circuit board under the tonearm. Remove the cartridge sled and look up under the tonearm end. You will see the circuit board the contacts are always black from tarnish. Use a pencil eraser to clean them up until they are shiny. You should also clean the end of the pins on the cartridge sled and while your at it check the tags on the end of the cartridge sled wires. If those are black from tarnish use a solution of backing soda and water and a old tooth brush to clean off the tarnish. Finally check the rca cable ends if those are the original black and white ends they loose there plating over the years and usually need replacing at this time. I hope something here helps.
Thank you. That's a wealth of great information. I'll do all you suggest, and do a D&C on the unit. The functions on this turntable are excellent, smooth and reliable, so the caps aren't likely an issue, but to be safe, I did buy that particular capacitor that makes the popping sound when it goes bad, just to be on the safe side. I mean, this is a 42 year old turntable, so it's bound to fail at some point. I'll swap out the cartridge and see if that doesn't improve things, but to be frank, the original owners barely used it in all the years they owned it, and the stylus is literally in pristine condition. Even the belt is still supple and in good working order. I grabbed this when I saw how well it functioned. I'll post the results when I finish with all the tips you kindly suggested. :P :D :P

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Re: Dual 1237 not delivering the best audio

Post by Tazzybehr » 31 Mar 2019 23:22

tlscapital wrote:
31 Mar 2019 22:50
What sort of connectors does the tonearm cables have ? Din, RCA... Likely if corroded or worn it/they could be replaced. This is a classic replacement that will instantly in many cases bring back the good sound in full.

If ever, a recabling (1 mete max, low capacitance and shielded) can be welcome as well. How about the inner tonearm wiring ? Is it still looking good and in place ? And the what about the cartridge and stylus, what are they ?
They are RCA cables, and they look to be in good condition. I will, however, clean them up. If the problem persists, I'll change them out for new connectors. I believe the original owners when they said this was hooked up, used a handful of times from when they bought it new in 1977, and then sat untouched until they finally decided to sell off their stereo. I didn't buy the Sony receiver despite it working well as I didn't feel like paying someone to do a total recap on it. Turntable worked great, though. I only noticed it's deficiency playing an Englebert Humperdinck album, as the horns that usually blurted out of my old stereo could barely be heard. My existing speakers from my old stereo are in excellent condition, checked them before I decided to keep them. It's not the receiver, so it's definitely the turntable I'm looking at as suspect. Hopefully, doing some of this will correct the issue, as I really would like to go back to enjoying my music without gritting my teeth...LOL.

The tonearm wiring looks to be sound. I don't see any breaks in the wiring, and there is no hum that you'd get from a bad ground. I'll have a go at cleaning the circuit board behind the sled, and going through and checking/replacing anything that doesn't correct the issue with a good cleaning.

Thank you. Very very much. :o :) :o

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Re: Dual 1237 not delivering the best audio

Post by tlscapital » 31 Mar 2019 23:45

You're welcome, but what brand and model of cartridge is that on your turntable now ? It could also be the stylus at fault. Are you certain the stylus is not somewhat damaged ? A single accident (forgotten by now) could do that. Finally, is the cartridge well aligned ? Is the overhang about right ? What about VTF, VTA, azimuth and the anti-skate setting ?

And after the big inside to outside the turntable plinth "clean", if the problem persist even after a cartridge swap, it could well be that your integrated preamp is either not right (depending on the cartridge you have now) or it could be failing as well. Although such symptoms as yours would do not really define a preamp mismatch or failure issue IMB.

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Re: Dual 1237 not delivering the best audio

Post by Tazzybehr » 01 Apr 2019 00:05

It's a Shure cartridge, original to the turntable according to the owners. I looked carefully at the stylus, it's literally in new condition. It sits properly on the records when it plays. I am not sure what VTF, VTA, azimuth are, but the anti skate setting is where it's supposed to be, according to the manual. I will, to be throrough, replace the entire cartridge with a good known I have on hand, and see if that doesn't change things. I have to wait until I get the receiver back (despite sounding great, the lamps needed replacing, it did need a cleaning, etc, and I didn't feel like doing the work). I'll post the results when I'm through with all the work I'm about to start with. Thanks much folks. !

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Re: Dual 1237 not delivering the best audio

Post by lbls1 » 01 Apr 2019 01:52

Definitely look at your cartridge, brand and model. You could experiment with a different cartridge, preferrably one with a better ranking than your current cartridge. I would tend not to suspect the tt if its in peak form. Be careful with cartridges as well, because they are often blamed for things that are not their fault. My Dual had a bit of a lackluster performance when I first hooked it up to my brand new amp. What changed things for the better was that I gave the turntable some listening time, where I was able to hear the rendering characteristics of the cartridge. I discovered wonderful abilities of the cartridge after a short while. I later changed the stylus for a new one, and it dramatically improved the sound with much better clarity and separation (the separation was already good on my cartridge).

I would first try a new stylus, and then if it hasnt brought significant change then try a new cartridge. Good luck.

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Re: Dual 1237 not delivering the best audio

Post by 62vauxhall » 01 Apr 2019 21:29

Directing your attention to the stylus is a good call.

May be just plain worn out or perhaps crud of some kind being caked on the stylus diamond . Happened to me a couple of times. The "contaminant" was pretty much invisible to the naked eye. Magnification revealed that just the very tip of the diamond protruded from the mass.

Can only speculate on what the coating was but it needed soaking for a while to soften before it could be brushed away.

Your description of what you were hearing was not unlike what I was hearing with an encrusted stoylus. Only that exposed tip was able to penetrate into the groove and the "foreign mass' rode on top of the groove walls.

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Re: Dual 1237 not delivering the best audio

Post by Tazzybehr » 07 Apr 2019 01:46

Well, I cleaned the sled contacts, the RCA tips, even cleaned the input female jacks in the receiver. It did somewhat improve the sound, but not a lot. So...next I'll replace the RCA male jacks and the cartridge and see if that doesn't bring me a little better sound. It's like those sharp notes want to come, but something is definitely holding them back...likely oxidation or a worn stylus.

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Re: Dual 1237 not delivering the best audio

Post by Tazzybehr » 07 Apr 2019 01:52

tlscapital wrote:
31 Mar 2019 23:45
You're welcome, but what brand and model of cartridge is that on your turntable now ? It could also be the stylus at fault. Are you certain the stylus is not somewhat damaged ? A single accident (forgotten by now) could do that. Finally, is the cartridge well aligned ? Is the overhang about right ? What about VTF, VTA, azimuth and the anti-skate setting ?

And after the big inside to outside the turntable plinth "clean", if the problem persist even after a cartridge swap, it could well be that your integrated preamp is either not right (depending on the cartridge you have now) or it could be failing as well. Although such symptoms as yours would do not really define a preamp mismatch or failure issue IMB.
I just got the receiver back from the shop, and it's in top condition. Caps are solid, all it needed was an alignment and circuit cleaning, along with deoxit, and normal maintenance items. The repair tech told me I made a great buy with this little amp, and that it should play well for some years to come. So the pre amp stage in the receiver isn't the culprit. It very very likely is the RCA jacks and/or the stylus/cartridge or both.

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Re: Dual 1237 not delivering the best audio

Post by Tazzybehr » 07 Apr 2019 03:18

Tazzybehr wrote:
31 Mar 2019 23:22
tlscapital wrote:
31 Mar 2019 22:50
What sort of connectors does the tonearm cables have ? Din, RCA... Likely if corroded or worn it/they could be replaced. This is a classic replacement that will instantly in many cases bring back the good sound in full.

If ever, a recabling (1 mete max, low capacitance and shielded) can be welcome as well. How about the inner tonearm wiring ? Is it still looking good and in place ? And the what about the cartridge and stylus, what are they ?
They are RCA cables, and they look to be in good condition. I will, however, clean them up. If the problem persists, I'll change them out for new connectors. I believe the original owners when they said this was hooked up, used a handful of times from when they bought it new in 1977, and then sat untouched until they finally decided to sell off their stereo. I didn't buy the Sony receiver despite it working well as I didn't feel like paying someone to do a total recap on it. Turntable worked great, though. I only noticed it's deficiency playing an Englebert Humperdinck album, as the horns that usually blurted out of my old stereo could barely be heard. My existing speakers from my old stereo are in excellent condition, checked them before I decided to keep them. It's not the receiver, so it's definitely the turntable I'm looking at as suspect. Hopefully, doing some of this will correct the issue, as I really would like to go back to enjoying my music without gritting my teeth...LOL.

The tonearm wiring looks to be sound. I don't see any breaks in the wiring, and there is no hum that you'd get from a bad ground. I'll have a go at cleaning the circuit board behind the sled, and going through and checking/replacing anything that doesn't correct the issue with a good cleaning.

Thank you. Very very much. :o :) :o

It's a Shure M93E. I've just ordered a replacement stylus, we'll see if this helps at all.

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Re: Dual 1237 not delivering the best audio

Post by Tazzybehr » 07 Apr 2019 03:23

Tazzybehr wrote:
31 Mar 2019 23:12
musicmn wrote:
31 Mar 2019 23:00
Hi Dave, the caps used in this turntable are only for the motor. And when they go bad you can here a popping noise from your speakers when the turntable turns off. Another issue if the caps are bad would be the motor jogging back and forth or the motor spinning backward on start up. There is a mute switch in line with the tonearm wires and rca cables. The contacts do get very tarnished over the years and this might account for the muffled sound. But my guess would be either a bad stylus or a very dirty stylus. It could even be a bad cartridge but usually they just go bad. Another place that needs cleaning is a small circuit board under the tonearm. Remove the cartridge sled and look up under the tonearm end. You will see the circuit board the contacts are always black from tarnish. Use a pencil eraser to clean them up until they are shiny. You should also clean the end of the pins on the cartridge sled and while your at it check the tags on the end of the cartridge sled wires. If those are black from tarnish use a solution of backing soda and water and a old tooth brush to clean off the tarnish. Finally check the rca cable ends if those are the original black and white ends they loose there plating over the years and usually need replacing at this time. I hope something here helps.
Thank you. That's a wealth of great information. I'll do all you suggest, and do a D&C on the unit. The functions on this turntable are excellent, smooth and reliable, so the caps aren't likely an issue, but to be safe, I did buy that particular capacitor that makes the popping sound when it goes bad, just to be on the safe side. I mean, this is a 42 year old turntable, so it's bound to fail at some point. I'll swap out the cartridge and see if that doesn't improve things, but to be frank, the original owners barely used it in all the years they owned it, and the stylus is literally in pristine condition. Even the belt is still supple and in good working order. I grabbed this when I saw how well it functioned. I'll post the results when I finish with all the tips you kindly suggested. :P :D :P
I took an eraser to those contacts at the back of the headshell and I got them to shine again. It did marginally help the highs, but I'll see what happens after I replace the stylus and the RCA jacks. Those jacks are experiencing the plating coming off, so that's probably where i'll find the culprit. I lightened the pre-existing cartridge and stylus to as light as humanly possible. Without the scale (mine was stolen some time ago), I'm going to have to eyeball the weight once the new stylus comes in. I just would rather not risk my records if this one has gone south.

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Re: Dual 1237 not delivering the best audio

Post by noisefreq » 07 Apr 2019 14:50

Tazzybehr wrote:
01 Apr 2019 00:05
It's a Shure cartridge, original to the turntable according to the owners. I looked carefully at the stylus, it's literally in new condition. It sits properly on the records when it plays. I am not sure what VTF, VTA, azimuth are, but the anti skate setting is where it's supposed to be, according to the manual. I will, to be throrough, replace the entire cartridge with a good known I have on hand, and see if that doesn't change things. I have to wait until I get the receiver back (despite sounding great, the lamps needed replacing, it did need a cleaning, etc, and I didn't feel like doing the work). I'll post the results when I'm through with all the work I'm about to start with. Thanks much folks. !
If you have a dull, lackluster sound coming from a Shure on a Dual I would suspect alignment issues.
Specifically vertical tracking angle.
Instead of spending money on caps and styli look at getting a Dual overhang gauge tool.
Your Shure M93 should work well with the Dual cartridge sled.
Is everything original? Platter mat, cartridge sled, table set to single play height, cartridge wired in phase?

Cleaning the contacts and inspecting the stylus are good ideas but proper alignment is crucial for optimal sound.

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Re: Dual 1237 not delivering the best audio

Post by Tazzybehr » 12 Apr 2019 23:06

Yes, this turntable is totally original. I am waiting for the replacement stylus, as I'm noticing some of my vinyl is skipping, so there is likely some sort of damage to the needle. I've got it weighted to just a hair above 2 grams (according to the settings, I don't have a scale) Platter mat is perfect and original (not dried rubber). The turntable was pre-set to single play (the original owners never used the auto spindle, didn't even know what it was for), and the cartridge came to them wired from the factory, and it's never been touched by anyone (I called them and asked). Now, I understand what an azimuth is after looking it up. Is it better to get one of these, or should I get this from Ebay: Pats Audio TK-14 Cartridge Alignment Gauge for Dual Turntables? I am going to replace the RCA jacks, as these are definitely suffering from plate loss, and I'd rather make sure I've got good conductivity going into the amp. I'll Youtube for video tutorials on how to use an alignment gauge and azimuth to see which will do a more effective job and post the results when I get them. Thanks so much. Dave.

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