Marantz DD running a bit slow

[dav305z]

I have my Marantz set to it's fastest pitch, and I think it might still be just a tiny bit off. It's not unstable, thanks to a pot cleaning, but still isn't running quite fast enough. It's nothing that you would notice unless your listening to a sustained high note, and even then, it's not dramatic.

What could be causing it? Could the pots just be shot? If so, is there a way to replace them? Could it be the motor? If so, is there a way to clean/lube that? How?

The table was a freebie, so I don't want to spend a ton of money getting this right, but at the same time, I love the table for the way it looks and sounds, and don't want to just chuck it and start over.

Any suggestions?

[basite]

wich tt is it exactly,
did the problem come suddenly? or did it gradually come.



Greetings,
Bert.

[dav305z]

Marantz 6170. I found her in my uncle's attic, and when I first tried it, it was way off. Now, after more playing time, and a pot cleaning its stable, but from what I can barely tell, a hair slow even on the tt's highest pitch setting.

One of the ways I figured out it was in fact, a little slow was by playing a song on the tt and in itunes. I started out with iTunes about 0.5 secs to 1 sec behind, but the end of the song, the iTunes version was slightly ahead.

Is the slowness more likely because of ruined pots, or is the motor just showing its age?

[royphil345]

No strobe display to set the pitch by?

If not, you can print a strobe disk. http://www.extremephono.com/free_turntable_strobe_disk.htm

There is 90% of the time another mini pc board mounted pot to set the range of the pitch control. Clean and adjust that, you should be in business. Any switches may also require cleaning.

Some direct drives have a standard center bearing you can easily add a couple drops of oil to (and should occasionally), or clean out and add fresh. 30 weight synthetic oil is a safe bet. If you can lift the platter and see where the center shaft goes into the bearing, add oil there. Some direct drives have different bearings that are harder to get to and are usually claimed to be permanently lubricated.

[dav305z]

It has a strobe that shows it running slow, but given the tt's age, I didn't really know how reliable it was.

[royphil345]

Ahhh....

If it's just a bulb that pulses with the AC current, it will be accurate. Some tables use an electronic circuit to control the light source. On these tables, the same row of markings is usually used for the 33 and 45 speeds. These can drift out of spec and be recalibrated. You'd usually only find this on a quartz-locked table... and not all of them...

A part has probably drifted slightly out of spec in your table, but it will probably work fine if you find that PC board mounted pot inside and gently adjust it with a screwdriver until the platter turns at the proper speed with the pitch control near it's center position.

Getting inside of a turntable usually isn't very hard. Remove the platter and counterweight. Secure the tonearm. I usually just leave the dust cover on and flip them over on a towel to work on them. Might have to loosen the PC board the pitch control is on or a PC board it's wired to in order to find the adjustment pot.

Many tables that use only one pitch control knob for both the 33 and 45 RPM speeds have a pot on the PC board for each speed. Allows adjustment so that the pitch control won't have to be adjusted much when you change speeds. It's never perfect though...

[dav305z]

Have the table apart fine, found a pot for each knob, but none mounted on the PC board (each pot has one wire connecting to the board, and another going directly to the motor). Not to sound too stupid, but how do I adjust the pot?

[royphil345]

Are you just looking at the back of the pitch pots?

What you hope to find are one or two mini pots on a PC board that fine-tune the pitch pots. They'll look something like the two round parts on the bottom of this PC board. http://72.4.160.82/gibson/media/CK191.jpg

They may just look like thin, round metal disks with a small screwdriver slot in the middle. Be careful, they are delicate. If you find some of these and mess with the adjustment a bit, you should be able to get "up to speed". On a simple, non quartz-locked turntable, there's really not much else they could adjust besides the speed. There's really nothing else that could get messed up by experimenting...

Hopefully your turntable has this adjustment. Not sure if it would, since it sounds like you have a separate pitch control for each speed. I haven't taken apart a turntable like that yet. Most DC turntables with a single pitch control for both speeds will have the PC board trimmers.

Good luck!!! Hope it works out for you... Crossing my fingers...


EDIT: If you bridge the two connectors on the pitch pot that the wires are connected to while the pot is at the fastest setting and the table speeds up further, the pot is bad and replacing it will solve the problem.

[basite]

I just checked with mine (I also have 2 seperate knobs for speed adjustement),
I can do the speed adjustement, there are just two of those things in there which you can each turn seperately, pretty much the same as a tt with one control for both 33 and 45...

I've just finetuned mine btw... :ihih:

keep them spinning,
Bert.

[royphil345]

Cool... Sounds like there's hope then...

We'll have to wait and see if dav305z has any luck.

If he doesn't come back... I'll know I got him electrocuted... Could I get in trouble for that???

[dav305z]

Hahah, you didn't get me electrocuted. I got in there, fiddled with the pots a bit, but being the gifted electrician I am, accidently pulled the wire connecting to the PC board. I'll solder it back on Sunday.

While I have the pot out though, would I benefit from just putting a new one in? Do I need to buy a specialized one for the Marantz, or is it simply a matter of going to Radio Shack and finding one with the same specs?

Also, I had the motor open. Would that benefit from a drop of oil, even though it's direct drive?

[royphil345]

A drop or two of oil anywhere there's a pivot point probably wouldn't hurt anything...

Sorry to hear about that wire. Shouldn't have any problem soldering it back in. Just don't apply too much heat for too long and fry the traces on the PC board (even that can be repaired). Strip the wire and twist it nicely. Push it through while melting the solder clogging the hole from the other side. Applying a tiny bit fresh rosin core electrical solder while heating the connection again after the wire is through will insure a good connection.

Replacing the pot is probably not necessary if the turntable speed is steady. TV tuner cleaner or contact cleaner / lubricant is excellent for spraying into pots to clean and lubricate them. Pricey though. The biggest problem with replacements is finding something the same physical size, with a suitable length shaft and that the original knob would fit on... The only difference in pots is their resistance value. It may be printed on the pot. Otherwise, you'd need schematics or a service manual for the table to find out. You could turn it to it's minimum setting and measure the resistance with a multi-meter. Pots are also available in linear or audio taper. The difference is in how quickly the resistance increases as the knob is turned. The pitch control is probably a linear taper.

Marantz probably wouldn't have parts for that table anymore...

Sorry to hear about your setback. Happens to all of us...

Hope you get it working!!!

[jrhymeammo]

Vintage Marantz with speed troubles? Sounds familiar, but mine was the 6100. Was it made to be played in US?

Maybe the spindle has been played/rubbed too much and became smaller in diameter. Then no tape would ever help. Hope you'll get some wax spinnin soon.

JRA

[dav305z]

Well, I soldered the old, clean pots back in, and it all worked perfectly - for about five minutes. The 33 RPM was controlling speed very well - fast being fast, slow being slow, and then the platter just slowed down almost to a complete stop. Set it on 45 RPM, and all is well again. I'm thinking the 33 RPM pot is shot - any other possibilities (I checked my soldering)?

EDIT - Well, I jiggled it a little, and it came back online, working perfectly right now. I'm guessing this isn't going to be permanent. Should I be looking for a replacement pot?

[royphil345]

Well, I jiggled it a little, and it came back online, working perfectly right now. I'm guessing this isn't going to be permanent. Should I be looking for a replacement pot?

Glad to hear it's working. Glad to hear you figured out your hum problem. I thought it was probably the preamp.

Sounds like that pot maybe could use replacing. I don't know if you sprayed a good contact cleaner / lubricant inside of it and worked it in. Stuff costs more than a new pot anyway... The value may be printed on it. If you have a multi-meter, you could test the resistance of the working one when the knob is set for highest resistance. It's probably the same as the other one. If you can't find something that fits the required space or the original knob, you could mount one anywhere if the wires are long enough... or if you make them long enough... Leave the old one in place for looks...

[dav305z]

The pot reads "5kΩB." Can someone translate this into English me? I couldn't find one at Radio Shack with these specs - where can I find one online?

[royphil345]

It's a 5k ohm pot. Most likely a linear taper (not audio). Not sure what the B would mean... Might just be a style or size indicator for that manufacturer. All they do is add an adjustable amount of resistance to a circuit. Up to 5k ohms max in the case of yours. Wattage rating is just what it will handle without burning out. Buying a pot the same physical size or larger should prevent any problems there. Problem will be finding one of suitable size with a suitable shaft. Shafts can be cut. That would usually require going knobless or buying a knob with a set screw. http://www.radioshack.com/product/index.jsp?productId=2102789

http://www.mcminone.com/product.asp?catalog_name=MCMProducts&product_id=28-0678

http://search.yahoo.com/search?fr=sbc-web&tab=&p=5k+ohm+linear+taper&btn=Search

There are a ton of electronics places on the web... Parts Express... MCM electronics... allelectronics.com... Most of the online electronics places seem to have minimum orders or a service charge on small orders though.

Good luck in your search!!!

[dav305z]

New pot seems to have fixed it. The old Marantz has looked better, but sounds terrific and that what I care about. The Grado and the Radio Shack deliver some pretty sweet bass for a budget setup.

Thanks for everyone's help.

[royphil345]

Cool!!! Glad you were able to get it all working.