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Second MA-6100 is a DUD!!!!

 

Ben Davis
Unregistered guest
I must have horribly bad luck or something. As I had posted in another thread, I bought a McIntosh MA-6100 which worked for a little while before having a constant static noise even when no music was playing or anything. Today I got my second McIntosh MA-6100 today and it looked to be in great condition (other than the messed up glass, which I knew about). I waited for it to warm up, it was cold after being shipped.

Once it felt like it was room temperature I hooked everything up to make sure it worked ok. The volume control felt dirty and made a little noise when I was turning it, but after a few rotations that went away. I then put some music on. It sounded horrible and distorted. I tried rotating every knob, changing to different inputs, I used to different sources as well as two sets of speakers, same results. Thank God this guy has a 3 day return policy. I'll be sending it back for sure. I guess that kind of limits what I can do to get a working one. It looks like I'll probably just wait for ebay and squaretrade to get back to me then get the first repaired. Oh well, I suppose it could be a lot worse.
 

J. Vigne
Unregistered guest


Ben, your Karma must be out of whack right now. It is quite unusual for a 6100 to have the problems you're experiencing. Don't give up, the Mac is worth the effort.



 

Ben Davis
Unregistered guest
I only wish I knew what I did wrong to deserve this.... I guess this will just make the end result a whole lot sweeter and more rewarding!? (trying HARD to look on the bright side of things)
 

Ben Davis
Unregistered guest
I'm not sure if this makes any difference, but I was playing around with the first amp to see if I could pinpoint the problem and I decided to not connect the jumpers (pre to power section of amp) to see if I could pinpoint the problem, and the static was the exact same as when they were connected. This leads me to believe that there is a problem with the power amp section and not with a dirty pot in the pre amp section, correct? My guess is that would probably make the amp even harder and/or more expensive to fix. Am I also correct in assuming this?

Thanks much for the help.
 

J. Vigne
Unregistered guest

Let's see if I understand what you did. You disconnected the pre to power amp jumpers. That left the power amp connected to the speakers with nothing driving it. Correct? With no signal appplied, there was still a static noise coming from just the power amp section? Just sitting there with no signal there was noise from the power amp?

If that's the case, you have isolated the problem to the power amp section. That's a start and a peculiarity if the problem went away even temporarily when you moved the input selector to tape head.

This is the problem you described in your original thread:

"There is a lot of static coming out of the right speakers. The cones seem to be moving a lot."

Is that still the case? The woofer cone on one or both speakers is moving in and out? Does this happen with the pre amp disconnected? Is the static only coming from one channel? But both speaker's woofers are fluctuating? Slowly or rapidly? Static implies the sound of a radio station not tuned into properly. It is a mid to high pitched crackling sound. Correct? Is there any low frequency sound you hear?


 

Ben Davis
Unregistered guest
Yes, you have what I did correct.

This crackling sound (what I called static) is still only coming out of the right speaker. It may have come out of the left at some point, I can't really remember, but right now and initially it was just coming out of the right. It started out faint when I first started having the problem but has since intensified. Both speakers woofers were fulctuating when I had the PSB Image 4t's hooked up, but I disconnected them and hooked up cheap speakers where I cannot see the actual cones for fear of damaging the speakers. The cones were fulctuating fairly slowly but not extremely slowly. All of this sounds exactly like a radio not tuned in and there is very little if any low frequency sound. If there is, it is the same type of sound and is very very faint.

I did talk to someone who works on these and he seemed to think that the problem was a lot different than the dirty pot thing the seller tried to tell me it was. He said that it was something that may come and go (which it has, sometimes there is no problem, sometimes there is, sometimes, I think, there is the sound coming from the left channel, sometimes it is not). He said that this was an unlikely thing to have happen during shipping and the seller would've known about the problem had he been using the amp at all.

Sorry about the poor grammar and puctuation. I'm just trying to type everything I've picked up on the situation at once.

Thanks very much for all the help.
 

J. Vigne
Unregistered guest

It's impossible to accurately diagnose the problem until it is put on a bench with the proper test equipment. Here's my best guess from what you've told me.
Problems that exist in both channels equally tend to be in areas that are common to both channels. In the case of the 6100, I think that would limit the area to the power supply. The woofers moving in and out indicates the likelyhood of a bad power supply capacitor. This is not unlikely in an amp of this age. It is a good idea to have the power supply caps changed as a matter of course when you purchase an amp this old unless you know they have been changed recently. My guess is the power supply caps will run about $20+ for each cap. Likely to be two caps that need replacing.
When things occur in just one channel, or one at a time, the problem is probably isolated to that one channel. The crackling noise sounds like there might be a bias resistor and a diode that are about to go out. This could also be a matter of a bad solder joint. A bad solder joint will often act like a diode and upset the whole mix of voltages in the amp. Either way the problem is probably made worse by the amplifier heating up and cooling down with use. If it is a bad solder joint it could go on like this for a very long time. If it is a resistor ready to give it up, the results can be quite devastating to the transistors downstream. This means the power transistors and they will be expensive to fix if they are destroyed. Probably about $40-70 each pair. Right now the parts for the repair are probably not that expensive. If you continue to use the amp without repairs being made, you are asking for the parts cost to go much higher.
The amp is not going to get better so I suggest you stop using it until it has been repaired. You can negotiate with the seller but only you and the seller know what the actual arrangements were for the sale. Whether the seller was aware of the problems is a matter for the technician to decide when it is put on the bench. Until you get, at least, a diagnosis, there isn't much you have to go on. With a diagnosis you can negotiate from a better position.



 

Ben Davis
Unregistered guest
Thanks for the response. I will definetely not use the amp until I get it repaired, since I've had the problem I've only had it on a few times (lasting a couple of seconds each) to test it.

Do you think it would be a wise move to have whoever ends up repairing the amp to replace some of the other things that tend to go bad, or should I just wait until stuff actually fails to get it replaced?

Thanks much
 

J. Vigne
Unregistered guest

If you send the amp to a restoration service, they will tell you what, after loooking at the amp, should be replaced. The situation is like taking a 30 year old car in for service. There are items that can go out, but, it is unlikely you will know that until they actually go out. Resistors fall into this category as they will change value over time and any that are out of value should be replaced so they don't place any stress on components downstream. But, a resistor will eventually "open" as opposed to a capacitor that will change value due to leakage over a period of time. Any caps that are suspicious should be changed with the overhaul. Power supply caps are the most likely to go first and do the most consequential damage. Coupling caps should be changed if the test bench indicates they are severely out of spec. There is no real way to tell if a cap is bad unless there is physical evidence of leakage. A cap can be bad and not leak however. A usual audible indication of a bad cap is the low frequency information or 60 cylce hum that will result. Diodes are like light bulbs, they either work or they don't for the most part. Your problem is likely to be a power supply or coupling cap that is leaking voltage and putting a stress on the later stages of diode and resistor. If the cap is bad and left unattended it will eventually leak badly and cause the diode and resistor to open like a burned out lamp. Components that have been under severe stress might be wise to change as they may be out of spec as a result. The tech will make this call. Transistors either work or they don't. No need to replace a driver or output transistor until it actually goes out.

The thing to keep in mind is the major portion of the repair bill will be the time the tech spends inside the amp. The parts cost is likely to be minimal compared to the labor. So it is wise to have as much done as the budget allows while the amp is on the bench. It will cost less to replace now than when it a resistor fails later and the tech has another $65-75 check in fee to replace one item.

Ask about warranty on the amplifier after the service is completed. Many techs won't give much of a warranty on amplifiers this old. If they are sure of the components that they find and replace then the warranty is usually longer and more comprehensive.

There are also restoration services that perform major component upgrades when they service an amplifier like the 6100. Old paper in oil caps and carbon resistors are removed and replaced with poly caps and film resistors. Of course this is going to be more expensive and will change the basic character of the amp. Rather like putting a new fuel injected, computerized motor and transmission into a '65 Mustang. You have to decide what you want to spend when you get into a venture like that type of restoration. And, you should have some idea what you want the amp to sound like when you are done with the changes. I would advise here to get the amp up and running as best as it can, and, then you can decide if that type of service is what you want to do.



 

Ben Davis
Unregistered guest
I'll keep all of that in mind. I'm going to call a few places tomorrow and hopefully find someone willing to work on the amp. I guess I will just tell the tech to replace anything that looks to be at risk. Hopefully they wouldn't try to trick me and replace things that didn't need to be replaced. I don't think I'll get the amp restored, just repaired. Hopefully this is all it will take to give me years of life in the amp

Thanks.
 

Brian Levy
Unregistered guest
Ben,
Are you on AA? I saw a 6100 over the weekend that was under a conditional contract. The deal haas fallen through and I'm now negotiating to buy it. It even includes the original slant leg case. Sound is as I remember them. Not quite as good as my C28/MC250 but not far off and better than any receiver I have. I'll probably permanently mate my Philips 6731 tuner to it or altrnatively the Fisher TFM300 that has more of a tube character and the Advents. Again key for me is local purchase and I can confirm its heritage. The seller is dumping it since it is the "cheapest" item in his collection and he prefers tubes. His basement looks like a high end stereo saloon.
 

Ben Davis
Unregistered guest
Yes, I am on audiogon. I have bought and sold a few things that I thought I wanted but never ended up using on Audiogon. I bought my MA6100s on ebay (a mistake that I will not make again). One I have (thankfully) been able to send back, but the other I had to get repaired. I took it to Almas Hifi in Royal Oak, MI.

I saw the MA6100 on Audiogon that you speak of. It's kind of too bad that I didn't wait for a while, I will end up paying more for my MA6100 and there is no case. Hopefully I will get it back fairly soon.

Right now I am trying to figure out which speakers to buy. I auditioned some B & W 603s, Spendor s3/5, and NHT sb3s. The B & W speakers were absolutely horrible compared to the others. The spendors were obvously a lot more detailed but the NHT were more full range. I still want to audition Dynaudio 52, they might be the happy medium. It may come down to me asking myself if I really need a pair of speakers as expensive (there are pretty pricey for me right now) as the Spendors. No doubt they are great speakers though.
 

Bronze Member
Username: Simplymcintosh

Post Number: 16
Registered: Jan-05
Ben,

Did you get the 6100 back, yet? Hopefully, you are getting great enjoyment out of it right now.

I have purchased some Spendor S5e speakers to pair with my 6200. Should have them in a week or so. They'll replace B&W CDM1 NT (predecessor to B&W 705) which I'll move to my office (but still running off the 6200).

Another forum member has S3/5 paired with a 6100 and loves the pairing. The S3/5 usually go around $500-600 on Audiogon. The newer S3/5se model is usually a little more than that.
 

Ben Davis
Unregistered guest
Sorry, I haven't really read anything much in a while. Yes, I did get the MA6100 back and everything sounds great again. I auditioned many speakers and the best I heard with Green Mountain Audio Europas. I auditioned them side by side with the Spendors as well as the Dynaudios and the GMA's were very close to as good if not better in every area and overall blew the others away (IMHO). I'll be returning to the dealer where I listened this weekend to pick them up, I can't wait.

Right now I'm trying to find the right cables as well as a turntable. I'm pretty set on interconnects but that's about it. Speaker cable is a little tough because the spring clips can only accept 14 awg cable and I'd prefer to go tinned or something rather than bare wire. I'm also a little wary of pins since it seems like they would decrease the contact area of the cable greatly. Any ideas?

...and for the turntable, I am thinking either Pro-ject 1.2 or NAD 533/Goldring GR1 (probably the Goldring). A rega is a little out of my price range but the NAD and Goldring are both p2 clones. Which would be best?

Hopefully it will all start to come together very soon, I can't wait to get everything and can really start listening!


 

mauimusicman
Unregistered guest
Ben, the Europa is a pretty amazing little speaker indeed. Glad you discovered them too. I love mine. I think you'll find they are more revealing of interconnects than speaker cables. Roy from GMA recomends the Audio Magic scorcerer cables.
 

Ben Davis
Unregistered guest
Yes, I emailed Roy a few times and he did recommend the Audio Magic ICs, unfortunately, they were a little out of my price range. Maybe someday... I went with Belden 89259 w/bullet plugs from Heartland Cables.
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