Marantz 2252b help

[brankovie]

The left channel on my Narantz 2252b dissappeared last night as I was listening to my TT. Upon closer listening I noticed that there is some sound comming from the left channel - about 20% of the normal volume. It was doing the same thing when listening to the receiver. Then I proceded to turn off and back on the amp and I heard a crackling -static noise fromt the problem side, the volume was normal for about a second and then it dissapeared. I tried the same thing several times with the same result. After leaving the amp turned off for about 10 minutes and removing other components from the top of it i.e. letting it cool down, it seemed to work normally. I did not have the time to listen for longer, but I suspect that it will come back or that bigger damage will occur.
What could be the problem?
Please take into consideration that I am not very well versed in the electronics terminology when giving advice - avoiding two letter abbreviations would be helpful.

Thanks in advance
Branko

[handy bob]

Many times intermittants are caused by a bad solder connection, agrivated by temperature changes or stress. Pull the covers and try tapping or applying light pressure in circuit areas of the left channel. Visually inspect all solder connections.
"handy bob"

[brankovie]

Thanks handy bob. I will try even though it is not really intermittent problem. Only in the sense that it comes back on after turning the amp off and back on. It never comes back on its own. Could the on - of switch have anything to do with it? Or the power input parts. (I apologize if it s a totally stupid question) The reason why I am asking is that when I turn the amp on it takes 2 - 3 seconds for it to actually come on and that after some clicking sounds (is that normal?) Also the left channel comes back after several times turning the amp on and off.
I know I am almost completely clueless about this stuff so I appreciate any help that much more.

Branko

[anatech]

Hi Branko,
Your fault is very probably the speaker relay. It's old and the contacts are probably pitted by now. You can test this theory by taking the top cover off the unit. Play it at a low level, and tap on the speaker protection relay. I'll bet the sound will cut in and out.

The relay contacts are made from a very thin plating of very conductive metal over a base metal. For this reason, you can not file or sand the contacts to restore proper operation. This may work for a very short time, but that's all. New relays may have contacts that are oxidized. In this case, spray some proper contact cleaner (or "WD-40" ) on a paper business card. Cut a thin strip and get it between the moving and stationary contacts. Move it back and forth (you should see a dark to black residue on the card). Once this is done, you must clean the contacts with a zero residue cleaner. Once dry, you can reassemble the relay. Don't expect this to work well with your current relay.

Understand that spray chemicals are tools. You can cause damage by getting it on or in the wrong place. Get any in the tuner section and you'll wish you never went into it. Even the dial lamps must be the 200 mA 8V types, 250 mA lamps or higher will melt the reflector. Understand that you have a really good receiver there. I have rebuilt many, and they easily outperform most new products. This set is very much worth it to have a skilled audio service technician go over it. It needs a fair amount of work to return it to it's normal great performance. Watch out for tweak artists, they will not help you out at all. While there are things that can be done to improve the performance, sticking in the cap-of-the-day will not get you there.

-Chris

[brankovie]

Thank you Chris.
I will try that as soon as I find out which part is the relay you are talking about.
(Are replacement parts available?)
I am by no means an expert on audio but i too can hear that this unit is very good. It even manages to smooth out my grainy cd player. The receiver is really good too.
I consider myself lucky because I bought it in a garage sale for $25. I spent many hours cleaning it inside out (the owner was a smoker and the receiver spent at least the 10 last years in a garage) but it was definitely worth it. After I have finally started to enjoy it this problem appeared. I am not at these DIY forums for pleasure but rather out of necessity if you know what I mean (even though I thoroughly enjoy it) so most likely it will be me doing any repairs. I will probably have to tap into your knowledge in the future.
Thank you again.

[EchoWars]

The 2252B will have either an Omron MY2-02-DC24 (DPDT), or a MY4-02-DC24 (4PDT). Should be fairly easy to find once you figure out which one you need.

Might mention that the front panel switches are also suspect and may need cleaning. You can give them all a workout and see if the channel comes back (as well as tap on the relay and see if that makes a difference).

[brankovie]

Thanks EchoWars,
do you think a balance switch (knob) could have something to do with it? It was dirty (noisy) so I tried to clean it by spraying appropriate cleaner/lubricant in it and turning multiple times back and forth but I don't think I was very succesful. I will do more testing today as it was too late last night to get into it.

Thanks again.

Branko

[anatech]

Hi Branko,
Rule #1
Never spray anything into a slide control!!
You may have washed out the lubricant, making the control forever sticky unless you rebuild it. For that, remove the control, carefully bend the tabs out of the way so that the phenolic part comes out. Be very gentle. Remove the lever / contact carrier and contacts. Now you can completely clean everything out of the housing and lever assembly. Gently clean the metallic contacts on the phenolic piece and the moving contacts with contact cleaner, then wash off that cleaner. Next, a light coat with something like Vaseline (with zero added stuff - like a fragrance) on the carbon tracks, and metallic tracks. Now for the fun part, apply some damping fluid on the inside of the housing and lever assembly. You need to do this to regain the smooth feel.

I'll bet that's the last time you blast a slide control with anything!

Now, what here is important to understand is that it is the metallic contacts that become noisy. The lubricant is there to prevent oxidation and to reduce wear. This is very important on the resistive material.

I'm pretty sure that set uses a two contact relay, but you will be able to see when you look at it. These relays are carried by most parts order houses, like Digikey for example. You will also need to know the coil voltage, probably 24 or 48 VDC (yes, they make AC coils for relays) for your set. I haven't looked at the schematic yet.

Switches. Leave them alone for right now. When you do clean them, use a proper switch cleaner, and only enough to get the job done. Switches have lubricants in them as well. Cheap "switch cleaner" is almost always going to cause trouble. Do not go cheap here, your receiver is far too nice a set to kill "just because". You scored big time, your purchase price has zero to do with it's actual value. If you attempt to justify a questionable approach with that, I'm outta here!

... so most likely it will be me doing any repairs.

Maybe some, but there are things that need doing that require both experience and test equipment. That is when it's far less expensive to use a good audio technician than to try it yourself, or have a friend hack away at it. If you want to get something done that is outside your competent ability, please wait until you have the money to get it done right. Everything seems simple to two kinds of people. Those who are real experts, and those who don't know much. All I'm asking is that you work within your own limitations in order to get that set up to it's normal performance at some point. Once it's fixed right, you will understand what I mean.

Last point. I think your tuning capacitor may require cleaning. This is a task that can easily ruin the capacitor, or surrounding parts. Be very careful none of the plates become bent! What you can do is blow any debris out with compressed air. Limit the air to about 50 ~ 75 pounds per sq inch and blow through the vanes. Never blow air sideways against the vanes, you may bend some. The large vanes with more plates are for AM, the smaller ones with a few are for FM. The oscillator sections are normally on the opposite side from the tuning string. Oh yeah, make sure you don't break the tuning string. Not fun to restring.

Hi Glenn,
How's tricks?
-Chris

[brankovie]

Chris,
first of all let me say that it makes me happy to meet someone with such affinity for my receiver model especially someone so knowledgeable. Believe me I really like my receiver and I do intend to keep and enjoy it for many years to come (hopefully).
Secondly, I do not think that everything is simple or that I know everything. I always do my homework and research diligently before doing anything. When I do something I try to be very careful. However, some information is not easy to come by - especially the type that is usually acquired through experience and is stored in heads of people like yourself. Consequently I do run the risk of doing harm, but I do try to minimize it through research and asking questions.
3. I found the relay (L703) and yes when I tap at it or push on one corner of it the volume in the left channel decreases with the tap or push. Right now it is working fine (both channels equal level) judging by ear (sound-stage). It is 24V DC relay. The type is not clear as part of the inscription is gone.
4. There is still the static crackle noise upon initial start up of the amp but it goes away within a second and does not come back.
5. The balance switch is not a slider control but a drum or turning knob or whatever it is called (English is my second language). I used a Radio Shack Control/Contact Cleaner & Lubricant "for electro-mechanical devices - especially drum-type TV tuners" (and it was not cheap) I was looking for the DE-OXIT stuff, but could not locate it around here. Actually I just tested the balance control and it is silent now, so I guess it worked?
5. When cleaning the insides, I actually vacuumed the piles of dust instead of blowing it out precisely from the fear of getting the dust in the wrong places (made myself a special tiny attachment). I then used denatured alcohol and cotton swabs to clean the nicotine-oil-dust mixture from everything I could reach. I did leave the tuning capacitor alone and did not spray anything in it. The tuner seems to be working perfectly fine as far as I can tell - it sounds good and the frequency indicator or pointer is right on the money.(Unless that crackling noise upon start up has something to do with it)
6. I do need the dial lamps - every other is out, but I have not seen the 200 mA anywhere and it seems that many people are using the 250 mA without any problems (just repeating what I've read).
Lastly you keep mentioning the things that need to be done to the amp to get it to its normal performance. What ,based on your experience, needs to be done? I do not have a point of reference i.e. another identical peace of equipment certified to perform "normally" so I do not know if it sounds less then normal or is on par with what it should be. I guess I could do some measurements as suggested in the repair manual and adjust the voltages etc. but beyond that I have no idea what else needs to be done?

Thanks again for all your helpful input

Branko

[anatech]

Hi Branko,
If you look at the bottom of the PCB where the relay is, you will see two pads for the coil at one end, then either two or four rows of three solder pads for the number of poles, or contacts for the relay. You can also normally see how many poles a relay may have by looking through the end opposite the coil.

The cleaner you used isn't very good. In fact, you may have caused issues that may take a while to show up. Remember, chemicals are tools. You must use the correct one for the job and use it properly. No way can I tell you more than I have already. The rest comes from apprenticing under a good technician. Radio Shack is not the proper place to shop either, you need to find an electronics jobber, or if you know what you need you can use Mouser, Newark or Digikey for starters.

It's a very good thing that the balance control is a rotary one. Most Marantz units use a slide type.

As far as the rest goes, no easy talk through is really possible. I could be glib and suggest you replace all the electrolytic capacitors, but who is to say the new ones are good (as good as the originals)? Then, it's possible to cause a lot of damage by soldering improperly. You must use 8V 200mA lamps. The 250 mA lamps will destroy the reflector in time. I've seen enough over the years. Of course, you could try to replace the lamps with flat EL panels. That would look really cool, aside from the fact that they run at low temperature as well.

There really is now way to tutor you via the internet, and it's difficult to tell good work from bad if you haven't been properly taught. One thing is for sure though, you must get the complete service manual somewhere and use that as a guide. It is extremely important that you do this.

-Chris