Teac x3r reel to reel troubleshooting help

[jasonguitar]

I have a Teac X3R that has a problem. I found this deck sitting on a curb completely intact a few years ago. I recently pulled it apart and cleaned, lubed, changed belts, demag-ed, etc. Transport works great. Direction controls work great. Heads are in nice shape. Plays back great. The problem it has is that when you first press play, a hum/buzz comes through the outputs but will abruptly go away at some point. Sometimes quickly, sometimes slowly. It will also come and go from time to time during playback. I found one burned up resistor across a relay so I replaced that but no difference. I figured it was dried up capacitors but I've replaced all the electrolytics in the power supply and about 80% of the caps throughout but the problem remains the same. Could a relay cause this type of problem? It seems like all the relays are functioning. Any tips?

[km6xz]

My advice is to never change anything until it is proven to be a problem, while doing repairs. If you repair it and all is in order, then consider rebuilding it. There is a big difference in the two distinct operations.
Which is it? Buzz or Hum? If a buzz it was not a capacitor "drying up". If hum, is it 120/100 or 60/50 hz? If it is a buzzy 60/50 hz there is likely a shield or ground contact that is intermittent. That can be found by mechanical vibration or light flexing of pc boards, cable bundles and connectors.
If 120/100 hz with the fundamental much stronger than any harmonics, monitor each supply rail with a scope to see which one of generating the hum. It could be from a circuit pulling too much current or a problem in the supply.
Does the hum/buzz vary with any gain controls? If not, look for the source as either supply or grounding in the output section. If the record level changes it look for the mode switching with an intermittent ground connection, the input preamp shielding, particularly at the connector etc.

The nature of the sound, and the influence of gain controls on it will tell you a great deal of what is causing it. It is not very often that 30 seconds of observation does not pinpoint the precise stage where a problem is in anything. That is one reason I harp on not changing anything that can introduce ambiguity or as often as not, introduce more problems, when just simple observation would tell you much more. In systems people understand more intuitively, they can see the illogic is bypassing that first step. An example no less to the point, a car which will not start does not often have the first step in repair of replacing all the shocks, everyone would agree.
Repairs can be frustrating enough without making it 10 times harder, 20 times more expensive, and 30 times longer by jumping to conclusions that do not fit ALL th data and observation. That is the #1 difference between a pro and tinkerer. One does less harm, in less time, with less risk to the unit. It has little to do with experience, education or available test equipment, it is a thinking process that uses logic and evidence as the #1 tool. Some of the people working on gear for money on this forum are not "pros" in this sense, and some amateurs are, it is all in their approach and reasoning even before a screw driver is picked up.

[jasonguitar]

Thanks for the lecture/advice. I believe you should not jump to conclusions and make instant judgements about people or electronics. Perhaps I should have provided a bit more information as to my methods to avoid such a totally uneccesary rant about "tinkerers" and "pros". Maybe you should ask more questions before you make such assumptions. If you strip away most of my statements, my basic question was "Could a relay cause this type of problem?" That's prety much all I wanted to know. I'm not a tape recorder technician. Vintage guitar amps don't have relays. If this was one of my main decks which I use everyday in the studio I'd simply take it to Adrian Pro Audio who is THE expert in Los Angeles and has serviced all my machines. However, for a deck that I found thrown away and thought it would be fun to "tinker" with, there are probably hundreds of techs on this forum who have worked on this deck or a similar Teac deck who could lend some experiential insight. The sound contains both hum and buzz which is why I described it accurately as hum/buzz. I DO know the difference and if it was simply one or the other it would indeed be easier to isolate. How could a shield or ground only open up when pressing play and then go away consistantly after a period of time? Along with a hum? Seems unlikely. It is not a vibration sensitive intermittant. Also, I didn't just blindly start replacing caps. I NEVER do that. I should have mentioned that the power supply cap reservoirs were bulging and the caps proved to be leaking when connected to a capacitance bridge. Obviosly they needed to be replaced first or I would never be able to isolate the hum part of the problem. If all the caps are the same age and some are failing, doesn't it seem likely that they should be replaced? LOGIC. Also, the nature of the sound coming on when the ouput amplifier is engaged and then going away is pretty consistant with the behavior of power supply caps which are drying up. Or perhaps a relay is sticky and only partially engaging at first but then eventually closes? The capstan belt had turned to goo. Was I supposed to not replace it first? Couldn't even fire the thing up without replacing it! Am I not supposed to lube the motors after they have been sitting idle for god knows how long? Clean the controls? I think my methods up to this point are sound and now we are at the next step.

[km6xz]

I am sorry if I concluded by the way you went about the diagnosis that you were not an experienced tech. As an experienced tech, however, the noise would have been a few second tracing so why ask such a question and provide no detail? The nature of the noise will tell a tech with electronics background what failure mode is occurring, what did a signal analysis tell you what the source was? And what made you focus on a relay out of hundreds of parts?
There is so little that you have revealed of your measurements that no one is going to guess specific causes. Where is the noise introduced, how far back does the path remain clean? Nothing in what you have said indicates that troubleshooting has been done, but instead focusing in on parts. You did not answer the specific questions about what controls influence the amplitude so no one is going to know where to point you.
Do a stage gain and path noise level measurement and the answer to where to look will be right in front of you.

The reason I concluded that you needed some basic suggestions on approach is that you started in on describing parts instead of repeatable measurements or symptom isolation. I have never seen a tech who could repair non-obvious routine problems who did it that way. Tinkerers focus on parts instead of analysis. Maybe you are the first competent tech who does however. Tube amp mechanics does not normally require in-depth diagnostic skills, which is the main reason so many people gravitate to working with old iron exclusively. A tech however sees no difference whether tube, digital, discrete, point to point, SMD, the diagnostics and physics are the same. The approach is the same in tracking down resolving problems which have not been seen before.

[jasonguitar]

It was a relay problem like I thought. Bad contact. I tend to have good instincts when it comes to troubleshooting even before doing a thorough testing process. Cleaned the relays and the issue is gone. I have had zero experience with relays as I've never tinkered with any relay equipped devices until recently. Sometimes I post a question like this because I might learn something from those who are more experienced and knowledgeable than myself and can cut to the chase if someone has had prior experience with the same symptoms and the same gear. Most of the time there are really cool, helpful people here and once in a while... not so much. Sometimes I ask a dumb question and in the process the obvious answer comes to me and this whole forum posting becomes part of my problem solving process. I am grateful for this valuable resource. Cheers.

[Gtr_tech]

I have a similar machine (X300R) that I ran for years. Never had a problem with it....it was rock solid. Head switching relays can cause racket when the contacts go high resistance.....basically opening the circuit at the head.