Sunday, November 17, 2019

Building my dream system (System #1, living room)

I covered a few months ago how I attained a bunch of vintage gear from my Uncle Rick.  I quickly purchased the other components I needed to make it work.  I got some speakers on craigslist and a receiver on eBay.

The speakers worked out great.  What an excellent purchase.  The turntable has had some odd mechanical issues but nothing that prevent me from using it and it too has been great.  However, I outlined early on that the receiver (an SR340) was giving me a ton of problems.  The FM tuner was wonky...I could get it going again but after a bit it would crap out on me again.  But more importantly (and I did not cover this in my original post, because I did not notice initially), I was having trouble with the 'phono' selector button.  I first noticed when I was listening to 'Three'.  I could tell something was muddy but it was subtle.  Finally I used the balance control to isolate the channels and noticed the left channel sounded horrible!  It was muffled and muddy and sounded like crap.  After some experimenting, I noticed that when I switched to 'phono', depending on how I depressed the button, it would actually sound fine, like it was properly 'engaged'.  So I got in the habit of sort of punching the button (with my finger) when I'd want to play a record, which is stupid because at this point I had given up on using the FM tuner so it was basically already always in phono.  At this point I started to determine that I needed to step my game up and get a working system.

But I toughed it out for a while longer and it seemed like the sound problem went away.  Out of paranoia I'd often check the channels using the balance control and both sounded really clear.  A miracle! Well, not quite.  One day I was listening to 'Dissident Aggressor' and during the chorus I realized that I could not hear the high pitched backup vocals! Now this damn receiver was playing the right channel out of both speakers! 

I took the whole thing apart looking to see if there was somewhere I could clean the contacts for the button but it is a more complex arrangement than I figured.  Eventually I decided that if I could replace the whole button it might work.  I even started to consider stealing one of the buttons from the other inputs which I didn't use, but then I realized that the phono button had a different number of contacts than the others.  This is the style of button in my receiver, but on a very different board.  

I did look at some individual buttons but at that point I was pretty bummed out on the whole thing and was starting to decide that I just wanted to replace it.  It is a pretty crappy receiver to begin with and I disliked a number of features, all of which was clearly implemented to save money.  So this is not a unit worth putting money into.

So I determined that if I bought a new receiver I had some criteria:

  1. has to be Marantz
  2. has to be a higher end unit that is worth taking somewhere to have fixed if necessary
  3. has to have a volume knob (old one had a stupid slider)
  4. has to have a VU meter or some other visual display with flashing lights and such
So I started searching on eBay for local pickup and came across the SR 8110 DC.  I loved this thing right away.  It had a 5 band EQ and a bunch of other bells and whistles.  

I found someone selling one (actual pic above) and I made an offer for $125 expecting a counter offer but they let it expire. I should mention the seller is in Blue Island IL which is less than an hour away.  I really wanted to do local pickup if possible because of not only the cost to ship, but the danger of damage.

Eventually I did talk to the seller :

But then I started to have second thoughts, and felt like I needed to shop around a little more, plus the guy made me wait a few days, plus an additional day and I really had wanted to pick this up on a weekend, and not during the week.  So I blew him off and went back to the drawing board.

I decided that if I was going to buy something that I wanted it to be tested and refurbished to some extent because I did not want to deal with any more problems right off the bat.  So I started hunting on ebay again and came up with something that looked almost two good to be true.  This is the actual pic from the auction and clearly not very good, better pics are below.

I was most impressed by the seller's extensive explanation of the unit and what he had done to it.

For your consideration is a Marantz SR-5100 that I have had for a lot of years.  When it arrived it had a blown power module (PM) (pins 8&9 shorted) and the AC plug was whacked off.  Both of the original power modules STK0050II (50 Watt) were replaced with Darlington Power Pack STK0080II (80 Watt)  It was used for quite awhile and then set aside.  It’s down size time and the Marantz was elected next to leave.  What’s been checked and adjusted to call it refurbished? Well, it got the dust blown out.  WHAT! you wanted MORE???????? Well OK!!
Tuner Section: 
The AM & FM just got the peak & tweak
In general I use HP 8648 & 3336C slaved to GPSDO (not necessary it’s just what I have),  RCA WR-52A, Tektronix 2465BCT, Fluke 87 and more.  NOTHING HAS A VALAD CAL STICKER
The tune up procedure in the tech manual looked good before I started but need a slight mod for setting the oscillators.  The “Full open and Full Closed” points left the slide rule pointer OOC.  Went back to what I have done since the end of the 50s.  Set the oscillators to the Max and Min dial markings.  The slide rule pointer now tracks just fine.
The FM mute level setting (with “FM Mute” was overly aggressive for the quality of the tuner at 12.5uV.  I set it at about 4uV and it unmutes full quieting and STEREO.  No use masking usable signals or having to put up with off channel noise.  Personally I leave the mute off so I hear everything anyway.
Signal level meter could not be turned off enough to just read full (5Points) at 500uV an absurd high level that also masked usable signals.  Another reason signal level meters are known as “Guess Meters” in other circles.  It is set  so you get a reasonable low end evaluation of signals
Tuning LEDs RED GREEN RED (meter) centered (GREEN) at center of FM STEREO decode.
Not part of tune up but I noticed the Mute was sluggish maybe a bit flaky compared to other units.  The FM chip maker NEC has a slightly different caps suggested for that part of the chip on their data sheet.  Putting in the NEC suggested caps made a BIG difference.  The original electrolytic caps tested OK but I have had lots of Electrolytic in audio service that would not work right test fine.
I also suspect the tune up instructions were “Cut N Paste.”   The old way with glue and scissors because of some wording.  This is NOT uncommon in SMs. 
POWER AMP check: 
Also tests the AUX input.
Power meter setting is specified 50W into 8 Ohms.  That’s 20V @ 1KHz or at 4 Ohms 14.1VAC @ 1KHz. Calibration pots bottomed out while still get the 50W LED at less than 50W.  50W seems to be about middle of the 50W LED not a bad thing
Power results: 
8 Ohms 1 channel driven wave form distortion on scope started around 19.3 VAC RMS on Fluke or about 91Watts.
4 Ohms both channels driven distortion of wave form started about 19.3 VAC or about 93 WPC
I suspect the limiting factor is the PM not the power supply from the above results.
Also I had been using a 2A AC fuse which promptly blew with both channels driven so I installed the specified 4A fuse for testing the PA and will include it in the box.  A new 2A fuse was installed after the 50wer setting
Pots and switches got DeOxit treated.  My experience with DeOxit over more than 30 years is you need to repeat it now and then.  I prefer to use a small syringe and large diameter needle.  The spray cans just make a mess and waste a LOT.
The brown stuff on the bottom of some boards is an OLD glue of some sort used to secure parts scabbed to boards most likely factory modifications that were not uncommon.
Power Supplies: 
Checked for AC ripple.  Nothing needed attention.
So what are the ISSUES?They are only cosmetic so Look at the pictures:
1) A couple of the grid openings in the top left of the case have been damaged and a small piece of wood glued to the inside for reinforcement.
2) The chassis around the power transformer has some what I think is moisture damage.
There are no electronic or mechanical issues I know of.
General Information: 
Those things we all knew back then but are not common knowledge now.
Most vintage amps are not immune to stupid.  Crank this one up past 50WPC 50 ohm or 63WPC 4 ohm something will fail.
Most likely first will be your woofs.  They sound real mushy when the glue on the voice coil melts and the coils start coming apart.  Old dry varnish on VCs fails faster than on newer woofs.
Got big CVs?  You can blow something amp easily enough.
The under rated 2A fuse installed may be little protection.
The rear accessory sockets are not protected by the fuse per the print.  One is switched and the other is not.  Plug a short into one and blow the cord or your breaker.  The other add the power switch to the list.

I corresponded after purchasing a number of times via email with the seller about music and audio and just life in general.  Steve is from Tennessee and was super helpful and just seems like a great guy.  I got the thing home and hooked it up and the heaven's parted - this thing sounds great!

I did finally get around to crimping a new spade terminal on my turntable ground wire because of course as soon as I dared to touch the wiring I had all kinds of ground hum but fiddling with things made it go away and now it is dead silent.  I kept the antenna from the SR340 and the tuner on this thing sounds amazing! Clear as a bell and very loud.  I couldn't be happier!

I love the VU meter.  The action on the tuner knob is satisfyingly 'heavy'.  At last I have a volume knob instead of a slider but unfortunately it is 'digital' - it increments and 'clicks' as you move it.  Still, I can live with this.  It has 3 tone knobs but just set at flat it sounds amazing.  At last I have achieved my dreams and I have a master system!

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