202-R Arrived

[audmod01]

Ron;

So noted! At the time I had it sitting on end with a block of wood under the side of the power transformer to help stabilize it. I also after some reflection realized that I have not cleaned the tube sockets nor the various controls either, so there are a number of things I still need to do. It all takes time, effort, parts, supplies and some amount of intelligence. There are some days I seem to be missing in the upstairs department. I can do some stupid things at times and later realize that I knew better.

One downside of all this is that in the last few weeks with my frequent work on radio chassis, I have discovered that I am allergic to the fumes from rosin flux in soldering operations. By the end of the day I am so stopped up that I have to resort to Zyrtec or similar medication and even Afrin nasal spray. I may have to invest in some sort of ventilation system in my study when I am working on electronic equipment. This is a real bummer! When I was young, I never had this problem.

 

[audmod01]

Ron;

About that relay, I seem to remember Dave mentioning that the relay is rather touchy about its mechanical tension. I had seen this before in other radios. The E H Scott 800B has some service notes about certain relays not wanting to operate and several methods of correcting that condition were discussed. Electro-mechanical parts are known trouble spots in electronic equipment. I have one Kenwood KE-7500 tuner that has one channel drop out once or twice a month on one channel. I narrowed it down to the function switch, but dread digging down into it to do the kind of cleaning that is really necessary to correct it. Every time I move the function switch it corrects the problem and will not do it again for weeks.

Joe

 

[dcgillespie]

Joe -- Glad the AM is alive! Some points to offer on the FM side:

1. If Silver Mica Disease is present, then regarding the signal strength meter indications, it will be limited to Z1 through and including Z4.

2. Is the Microtune circuit not tuning properly, not responding to the touch of your hand, or both? The hand sensing circuit is crude by today's standards: Basically, V10 (6EV7) which makes up the Microtune hand sensing circuit, is nothing more than an amplifier whose input you draw your hand close to. The resulting hum signal generated is rectified, and used to bias the relay driver section of the tube on or off. The Microtune sensitivity control is rather sensitive -- as is the location of the tuner. My 200B triggers with perfection in my lab, which is a linoleum floor on top of concrete. But out in the entertainment room, which is thick carpet on top of a thick backing on top of concrete, the triggering is OK, but hardly perfect, and requires a distinctly different sensitivity setting of the Microtune adjustment.

3. The 6AV6 is used in the Muting circuit, functioning as (about) a 3 mHz oscillator whose output drives the final limiter stage into cutoff when limiting action occurs. One of the biggest failure points is the on-off switch when it is part of the muting adjustment control. Just like the relay contacts in the MPX-100 I finished up, there's not enough current passing through the switch contact to keep them from becoming compromised over time.

4. When you check voltages, remember that the indicated voltages on the schematic are with no antenna, and neither tuner receiving any station. That condition causes the tuners to draw the most current, which can change the voltages from that of a strong reception condition quite significantly.

You will have this sucker licked in no time!

Dave

 

[audmod01]

Dave;

Thanks for those comments. I will be referring back to them as I look at the unit again.

The microtune circuit could be reacting because of my study. Like you, I am in a room with carpet, pad and then concrete floor under that. Cleaning of controls has to be one of the next steps along with cleaning of tube sockets. There may even be a few loose tube socket contacts. Some of the tubes do not seem to have a firm resistance as a tube is pushed into the socket.

It has been a long day, but productive.

Joe

 

[fred soop]

.....
I am allergic to the fumes from rosin flux in soldering operations. By the end of the day I am so stopped up that I have to resort to Zyrtec or similar medication and even Afrin nasal spray. I may have to invest in some sort of ventilation system in my study when I am working on electronic equipment.
.....

I'm not allergic but it is still not good to breathe any of this stuff or fumes from solvent based paint and glue used in model railroad work. A good remedy, though it may not be enough in your case, is to have a small fan blowing at low speed across the work area to keep the bad stuff moving away.

 

[audmod01]

Ron;

I can't believe how many ridiculous results I get on eBay if I search for LED replacements for #47 dial lamps! I tried a number of ways of describing what I want and I never get anything even close to what I am looking for - lots of car related stuff for 8V, 12V etc. Even a search specifically for 6V LED lamp replacements do not return what I am looking for. I would like to find the type of LED lamp replacements you installed in your 202-R tuner and am getting quite frustrated. If I search for Fisher dial lamp replacements I get stuff for Fisher Price equipment! Ugh!!

Joe

 

[mrphilco]

Joe

Try here:

http://www.pinballlife.com/index.php?p=catalog&parent=192&pg=1

DO NOT buy the 39 cent cheapies, they are designed for use in DC circuits only.

Scroll down to the Ablaze Premium Ghost Buster lamps in clear or frosted lens. These are brighter than the LED lamps I bought from the auction site...and the old fabric tubes may not fit over these.

Or, send me an email (you have my email address) with your physical address, and I'll send you a few of the "not as bright" eBay lamps if I still have any. Let me check... Edit: Yes, I have some more of these...not a lot but more than enough to send three to you, no problem.

 

[audmod01]

I just placed an order for tubes for the 202-R and for the Electra I am working on for my granddaughter. With new tubes I can eliminate tubes as a cause of low IF gain on FM for the 202-R. In the Electra it is getting a set of 12AX7 tubes for MPX and audio circuits plus IF tubes. In the case of the 202-R though, I really do not think the tubes are the issue, but I can at least look for other possibilities with confidence that I have already tried the tubes.

I have taken a break from work on both the last few days to deal with a plumbing problem that developed. A drain tube for a bath lavatory literally broke loose from the top chrome ring. Naturally repair of such issues never goes quite as easy as it sounds. I finally stopped the leak that existed today after new parts had been installed. Plumber's putty was required in a spot that normally would not have been necessary. This is in part due to a custom counter-top basin combination casting flaw. At least now I can get back to other things. At my age I am not fond of having to be a contortionist to repair plumbing, but if I can manage I still do so.

Joe

 

[gadget73]

Plumbing is the devil. Definitely one of my least favorite things to deal with. It all just seems so marginally designed that its almost amazing that it works at all. Last week at work I had some plumbing issues and I actually called someone. One of the pumps in the septic pit out front failed, and thats where I draw the line on what I will and will not mess with.

 

[audmod01]

Gadget;

I certainly don't blame you on that one. I steer clear of those issues too. We live in the country and have an aerobic system with air compressor and pump with sprinkler heads. I have had to rebuild the air compressor. A kit of graphite vanes for it was a little over$100 but a whole pump was nearly $600 plus shipping. I add chlorine tablets to the area where the pump is located, but those two areas are as far as I will go.

 

[gadget73]

I have a standard in-ground septic at the house. No pumps, it flows down hill. Figuratively, its pretty flat where I live. Every few years I have it pumped out.

 

[audmod01]

This morning I got around to connecting the 202-R to my Dynaco system using the spare input. There was no problem with the audio coming from the 202-R. Either the cables I used to connect to the Electra unit were bad (open ground) or else there is a problem internal to the Electra causing hum on its Aux input. The strange thing is that as soon as cables are disconnected from the 202-R going to the Electra, the hum goes away and can only be introduced by touching the signal lead of the coax audio cables with my finger. I will say that both units are plugged into AC receptacles in the same room, but may not be from the same source. There could be some sort of ground loop being set up. I need to feed both units from the same AC receptacle and see if that makes a difference.

It was quite reassuring to hear nice clear audio from the 202-R though. I also note that there is no interference on FM mono from the adjacent channel local station 4.5 miles from my house while listening to my favorite classical music station which comes in with a much weaker signal (-9dBm for the local, -59dBm for the distant station). I believe the extra IF stages in this tuner provide enough more selectivity that it makes a real difference compared to the other tube type receivers or tuners that I have. Kudos to the Fisher design team for the great design they developed!

Joe

 

[audmod01]

Just did a recheck with the 202-R connected to the Aux input of the Electra and it still has the hum even after connecting the two to the same AC outlet in the room. I even tried reversing the plug to one and the hum continues.

It hums because it doesn't know the words (a humorous saying of a friend I used to work with).

Joe

 

[audmod01]

Final recheck with the Electra and 202-R connected to each other - the audio cable I had used had a bad ground!! I tried another cable (both were new) and the other cable delivered flawless sound through the Electra, so both are actually OK! That makes my day!

Joe

 

[gadget73]

Done that, with a tuner actually. Unfortunately I happened to be using my big Phase Linear when it went open. 350 watts of hum through speakers rated for 85 doesn't go well. I melted the voice coils before the fuse blew, which happened before I could hit the power switch. That was probably the most expensive crappy cable I've ever dealt with. Further lesson learned, never run the big amp when doing stuff like that.

 

[audmod01]

The first time I tried the Aux connection to the Electra with the bad cable back to the 202-R I was just lucky I had turned the Electra volume control down and gradually brought it up. I ruined some speakers years ago with an amp that had far more power capability than the speakers could sustain. It also happened to pop the output transistors too - arrrrgh! Many dollars and more speakers later I finally got it working again. Lesson learned.

I noticed that the muting sensitivity adjustment had to be changed over a period of several minutes from cold start. I think this is due to a questionable 6AV6. One of its diodes does not have equal output level compared to its companion. It also changes in output level from cold, so it likely the culprit on the changing muting level situation.

For now I am going to concentrate on some improvements to the Electra 440-A/490-T mating.

Joe

 

[dcgillespie]

Open grounds and high power do NOT mix. Gadget -- you might remember that during the listening tests portion of the Bogen MO-200A project, I always used a separate independent "safety" ground connection between the preamp and the Bogen -- for the very purpose of preventing a couple of hundred watts of hum power from accidentally going to my Cornwalls in case the interconnect ground should fail. I've never lost a speaker, but have had a blast or two that concerned me enough that I use the safety ground for anything over 50 watts of power anymore. I have a Hafler DH-220, that I basically treat as an open can of gas. The last thing I want is that thing let loose through my speakers!

Dave

 

[audmod01]

Dave;

Can you elaborate about the independent safety ground? Is this a separate device you constructed or bought? I have been especially careful after my one experience with blown speakers. In the case of using the Electra as an output device I had it connected to speakers capable of handling over 60 watts per channel and the Electra's output would struggle to deliver over 12 or 15 watts - still could be loud enough to hurt one's ears though.

Joe

Joe

 

[dcgillespie]

Joe -- It's nothing more than a 10 ft length of #16 Ga stranded wire with the clips from one of the larger clip lead sets attached on each end. I simply clip each end to some point representing the audio ground (virtually always the chassis in my case since I deal with vintage equipment) of each piece in question. That way, even if you intentionally partially remove one of the interconnects, the ground integrity remains in tact. It is not intended to be a permanent piece to be left in place since it can cause ground loops with some pieces. Rather, it's simply a safety device used in test situations, until the integrity of the working ground connection through the interconnect is established and verified.

Dave

 

[audmod01]

Dave;

OK, I understand now. At first I was thinking some sort of active device. A heavy piece of wire is simple and achieves the objective.

Joe