Date   

Re: Posting Files

Paul
 

look in the files section I uploaded everything else I had specific to the SG80


Re: Kenwood KT-8300/9900 Tuner

rick.savas@...
 

Hi Joseph,

Re-drawing the schematic is a time consuming task, good for you, what are you using to draw the schematic?
The one scan I have is pretty good just that when you print them out they do not line up so fiddling with the print settings can make them line up. Not as tedious as re-drawing the whole schematic again.
One thing I noticed is that they use an RC4558 opamp, which is dual uA741, for ICg11,13, well that is probably one of the first mod's I could suggest to make. Just have be careful with oscillation using a faster part, since they did not use good local device decoupling. They used a metal can package, made the footprint a DIP. All the opamps on my spare X05-1350-10 pcb are JRC4558T dated 8003,8007
Since I have a spare X05-1350-10 pcb that is easy for me to look at if you need some help. I got it for a good price since many components are obsolete. I see they have a couple of parts tack solder on the back. I'd have to check if they are in the schematic.ceramic disc 473Z from #32 to ground plane for the section IF. The resistor is covered in glue, I'd have to measure that, from CN1(red wire) to R158, the other side of R158 goes to CN3-green. Of course CN1,2,3 are not labeled on the schematic :) More tracing, CN1,2,3 have a common connect on the pcb, which is the red wire, +15V. They do not show common on the schematic however if you follow CN1, it goes to B* at #21, I think, you know it is hard to trace with the dos we have. Best I can do for now.

Good luck Rick


Re: Kenwood KT-8300/9900 Tuner

Peter Wieck
 

For the record, I am so very glad that there are members here with enough time and thoughtfulness to dig so deep and provide key information for the rest of us!

Thank all of you for your efforts!

Peter Wieck
Melrose Park, PA 


Re: Kenwood KT-8300/9900 Tuner

Joseph Strickland
 

I have been re-drawing the schematic for the KT-8300/9900 models. The copies available on the internet are very poor scans of the original schematic. In the process I discovered that the caption about the signal level applied during AM alignment on the schematic page did not agree with that mentioned on page 7 in the AM alignment instructions. Page 7 was correct in stating that the signal level applied was at 30% modulation. On the schematic page(s) the caption about AM alignment says 30% DEV. or deviation. Deviation applies to FM modulation not AM modulation. I have corrected this on the schematic I am redrawing.

There are some areas of the original schematic that have trace lines so close together that they become quite blurred due to poor scans. This is particularly true in the area between ICg9 and Qg15 and the IF Trigger control. Also the ellipses that contain voltage measurements are just black with no discernible information in them. I see no notation on the schematic as to whether the voltages measured are with or without signal applied to the FM RF input terminals or the AM RF signal input. I need to examine statements on other pages of the manual to see if the conditions are stated. I would expect the condition to be with no signals being applied.

I need to open up my tuner and take time to measure voltages and develop a table for reference. I have deleted all the notations as to voltages in the schematic ellipses. I did leave the notations as to voltages provided to the power supply rails. Currently with the schematic page set for 11" X 17" and 300dpi plus color for the modifications a fellow member of this group added, the file size for that page is 48.2MB. I hope to get a print out at C size which will be 22" X 34" so I can work on the tuner without having to use glasses to read the fine print. After that I will see if I can reduce the resolution of the 11" X 17" drawing to get it to a lower file size that still will convey all the needed information without compromising the visibility of the information.

Joe


Re: Bruce Carter grunge filter

John Carpanini
 

Hi Radu,

  Yes , you are correct, each rail should be decoupled to Ground, not each other.  In effect the "filter" is shunting all that high frequency hash out into the ground plane.  Please post back with your results.
Regards
JohnC


Re: Bruce Carter grunge filter

Radu Bogdan Dicher
 

On further examination of the circuit, the op amps are ran in balanced PS mode. I may have to revise how I'm "grunge-decoupling" this. 

BTW - the ZD801 choice is very marginally sound - in my bench tuner, the zener was out of spec by about half a volt upwards, which therefore supplied the HA11211 (absolute maximum Vcc 13V) with just about 13.5V. I replaced it with a 12V zenner - in lack of a better matching part - but I came to think, btw, that the service manual incorrectly calls for +12V in the emitter of Q801. It should be +13V, to match the -13V on the negative rail. Either way, the zenner is spec'd too close to frying IC106 for comfort. I guess some drop over L102 dips it under 13V. Has everyone else noted this? 

Thank you,
Radu. 

On Sun, Dec 1, 2019 at 8:32 PM Radu Bogdan Dicher via Groups.Io <vondicher=gmail.com@groups.io> wrote:
Hi John,
And thank you for pitching in. In the case of this tuner, with its TA7136P, I went between pins 4 and 7 of each op amp with my "caps pack" - as visible in the picture enclosed. 

However, unless I triggered something totally unrelated, this seems to turn off any signal coming into the tuner (I get no indication of my generator's signal in by watching the tuning meter as I go over the adjusted frequency). The AP box doesn't sense audio signal coming in (the level adjusting relays would go off as I dial onto the generator frequency and past it). 

Busy with family and different projects (tube integrated indefinite lender for family member), so I didn't get back to this, but that's what's been going on the other day.

Thank you,
Radu. 

On Sat, Nov 30, 2019 at 11:07 PM John Carpanini <jacarp@...> wrote:
Hi Radu,
  If I'm understanding you correctly yes all of the caps are in parallel going from B+ to ground.  Ideally you want the hot side of the cap with the shortest possible lead and let the ground side run as needed.  Here's what Bruce had to say from one of his earlier missives:

"In decoupling applications, I have long been an advocate of multiple capacitors - each creating more rejection in the stop band. At the point of power entry,

an aluminum or tantalum with a resonance of about 100 kHz, then near IC's a 0.1uF for 10 MHz, in parallel with a 0.01uF for about 70 to 80 MHz, in parallel
with an NPO/COG 1000pF for about 400 MHz, in parallel with a 33pF NPO/COG for 2.4 GHz (to get rid of cell phone trash). The three ceramics create about
equally spaced nulls on a log frequency plot, keeping overall stop band impedance very low. Of course I'd love to see a capacitor manufacturer put all
of those inside a single package, but it won't happen because practically nobody knows how to properly decouple circuits - preferring to use a single 0.1uF - a
legacy value from the middle 1960s when computer boards ran at about 1 MHz.

 

I recommend a small series resistor in line with the + and - supplies, 1 to 10 ohms or so, with the bypassing right at the op amp power pin.  This vastly improves power supply rejection ratio of the op amp.  Also, at minimum, 33 pF NPO in parallel with the 0.1 uF cap to get rid of cell phone interference.  Adding other caps in parallel such as 1000 pF NPO will improve FM rejection in the audio circuit."

Regards
JohnC


Re: Bruce Carter grunge filter

Radu Bogdan Dicher
 

Hi John,
And thank you for pitching in. In the case of this tuner, with its TA7136P, I went between pins 4 and 7 of each op amp with my "caps pack" - as visible in the picture enclosed. 

However, unless I triggered something totally unrelated, this seems to turn off any signal coming into the tuner (I get no indication of my generator's signal in by watching the tuning meter as I go over the adjusted frequency). The AP box doesn't sense audio signal coming in (the level adjusting relays would go off as I dial onto the generator frequency and past it). 

Busy with family and different projects (tube integrated indefinite lender for family member), so I didn't get back to this, but that's what's been going on the other day.

Thank you,
Radu. 

On Sat, Nov 30, 2019 at 11:07 PM John Carpanini <jacarp@...> wrote:
Hi Radu,
  If I'm understanding you correctly yes all of the caps are in parallel going from B+ to ground.  Ideally you want the hot side of the cap with the shortest possible lead and let the ground side run as needed.  Here's what Bruce had to say from one of his earlier missives:

"In decoupling applications, I have long been an advocate of multiple capacitors - each creating more rejection in the stop band. At the point of power entry,

an aluminum or tantalum with a resonance of about 100 kHz, then near IC's a 0.1uF for 10 MHz, in parallel with a 0.01uF for about 70 to 80 MHz, in parallel
with an NPO/COG 1000pF for about 400 MHz, in parallel with a 33pF NPO/COG for 2.4 GHz (to get rid of cell phone trash). The three ceramics create about
equally spaced nulls on a log frequency plot, keeping overall stop band impedance very low. Of course I'd love to see a capacitor manufacturer put all
of those inside a single package, but it won't happen because practically nobody knows how to properly decouple circuits - preferring to use a single 0.1uF - a
legacy value from the middle 1960s when computer boards ran at about 1 MHz.

 

I recommend a small series resistor in line with the + and - supplies, 1 to 10 ohms or so, with the bypassing right at the op amp power pin.  This vastly improves power supply rejection ratio of the op amp.  Also, at minimum, 33 pF NPO in parallel with the 0.1 uF cap to get rid of cell phone interference.  Adding other caps in parallel such as 1000 pF NPO will improve FM rejection in the audio circuit."

Regards
JohnC


Re: Bruce Carter grunge filter

John Carpanini
 

Hi Radu,
  If I'm understanding you correctly yes all of the caps are in parallel going from B+ to ground.  Ideally you want the hot side of the cap with the shortest possible lead and let the ground side run as needed.  Here's what Bruce had to say from one of his earlier missives:

"In decoupling applications, I have long been an advocate of multiple capacitors - each creating more rejection in the stop band. At the point of power entry,

an aluminum or tantalum with a resonance of about 100 kHz, then near IC's a 0.1uF for 10 MHz, in parallel with a 0.01uF for about 70 to 80 MHz, in parallel
with an NPO/COG 1000pF for about 400 MHz, in parallel with a 33pF NPO/COG for 2.4 GHz (to get rid of cell phone trash). The three ceramics create about
equally spaced nulls on a log frequency plot, keeping overall stop band impedance very low. Of course I'd love to see a capacitor manufacturer put all
of those inside a single package, but it won't happen because practically nobody knows how to properly decouple circuits - preferring to use a single 0.1uF - a
legacy value from the middle 1960s when computer boards ran at about 1 MHz.

 

I recommend a small series resistor in line with the + and - supplies, 1 to 10 ohms or so, with the bypassing right at the op amp power pin.  This vastly improves power supply rejection ratio of the op amp.  Also, at minimum, 33 pF NPO in parallel with the 0.1 uF cap to get rid of cell phone interference.  Adding other caps in parallel such as 1000 pF NPO will improve FM rejection in the audio circuit."

Regards
JohnC


Bruce Carter grunge filter

Radu Bogdan Dicher
 

Hody all,
And Happy belated Thanksgiving to all those celebrating.

Needing some clarification on Bruce Carter's grunge filter. My understanding is this is a decoupling solution on steroids, covering just about anything that can infiltrate DC these days. Therefore, if intending to apply this, I'd get the power supply rails of the AF stages decoupled with something like 0.1uF/0.01uF/1nF/33pF in parallel, as close to the op amp (if applicable) as possible, on Vcc/GND. 

I am applying this to a Gamma I and get cancellation of signal in (no movement on meters, etc.). I don't think I am shorting anything to ground by adding these parts. 

Attaching pictures - I hope they hop on. 

Thank you for your input!
Radu.


Re: Posting Files

 

@Paul - I would appreciate a chance to view the Sencore Tech Tips.  


Re: Denon tuners

A- Mon
 

I would agree. The 1500RD was my first 'proper' tuner; I bought it new and was impressed with the sound at the time, but compared to the other tuners I have now from Technics, Audiolab, Rega, Linn (to name a few) it sounds flat and lacklustre. Also it only took a few years for the tuning knob to stop working reliably. Likely just needs cleaned, but I was usually happy to use the remote. Another bugbear for me is the very long mute time between each tuning step; not so good for dx'ing though I found the sensitivity to be fairly good. Aesthetically I am loath to sell the 1500RD just because I have always thought it looks very classy; from the all-metal case construction to the large bright blue dot-matrix display I just love looking at this tuner.


Re: Kenwood KT-8300/9900 Tuner

Joseph Strickland
 

Bob;

I think you are correct. I believe the word should have been multiplicative. A couple of search engines I tried suggested that the word was multiplicative. The black box demodulator circuit is large enough to contain all of the suggested parts. Kenwood may have chosen close tolerance parts including resistors, capacitors and an inductor to implement the quadrature detector outlined in the article referenced. One of the nice points about such a circuit is that it is relatively simple. .04THD is a very good distortion measurement.

For many years analog television manufacturers used quadrature detectors for their audio detection circuits. Most of them made the inductor a variable one which could compensate for drift or component tolerances of the other parts in the detector circuit. It was definitely less expensive than Foster Seeley detectors or Ratio Detectors as to construction of transformers and their alignment (multiple steps). It was easy to retune a quadrature detector after replacement doing it by ear.

Joe


Re: Denon tuners

regsrus2000@...
 

Thanks for that comment. I'm not sure I can tell any appreciable difference in sound quality between the 800 and the 1500RD. But I've been thinking of having both gone over by a good tech and brought to their best. Tech recommendations, anyone? If not publicly, I'm regsrus2000 at that yahoo place.

And thanks to everyone who has responded in this thread! I hope it will continue to be active.

David (in NC)


Re: Kenwood KT-8300/9900 Tuner

newaag
 

I think the manual has a typo from translation, and it should be multiplicative detector, (not multicative). 

A multiplicative detector from that era would be a form of quad detector, employing an active mixer to mix the two 90 degree phase shifted time domain signals to detect the audio.
Here is a nice brief overview
https://www.electronics-notes.com/articles/radio/modulation/fm-frequency-demodulation-quadrature-coincidence-detector-demodulator.php 

The other type listed there above (a form of pulse count detector) usually needs a mixer to take the IF to a lower frequency before detection. That type detector was used by Kenwood in that frame, in the 600T.  
Bob


Re: Denon tuners

gpdavis2
 

My brother still listens to the nice sounding Denon TU-720 I gave him for his b'day 25-odd years ago. Plays great with his 3.5wpc VM 1448 tube integrated amp and pair of Klipsch Forte II spkrs. I've had a TU-1500RD a time or two, but would fall into the 2nd tier of tuners for me, based on SQ. No telling what a recap and/or alignment would have done to improve things.


Re: Kenwood KT-8300/9900 Tuner

Joseph Strickland
 

Rick;

Yes, the .04 THD measurement you obtained is consistent with the specification listed in the advertising and service manual. For my situation the unit I have seems to be an excellent performer for intermod and selectivity. I have a local station broadcasting at 100.7mHz at 10kW only 4.5 miles from my house and my desired station is over 60 miles away at 101.1mHz. The local station comes in at -9dBm and the desired station at -59dBm. Using my outside FM-9 antenna pointing to the desired station with the undesired station on the back end of the antenna I get excellent selectivity even in the IF Wide bandwidth selected. In IF Narrow bandwidth the selectivity is even better. I have two Kenwood KT-7500 models which I repaired and one has two 180kHz filters for improved selectivity, but neither of those tuners can equal the quieting developed in the KT-9900.

I do not so far know of a more detailed explanation of the detector circuit used in the Kenwood KT-8300/9900 tuners. It may remain a mystery. I do know that there is some active circuitry inside the detector as it receives +13VDC from the power supply.

Have fun!

Joe


Re: Denon tuners

c n
 

I confess, I haven't opened the 767 because of other projects and was going from memory of looking at a schematic. My memory is obviously faulty in this case.  I will have to do so soon to check for leakage and accomplish battery replacement.
Chuck


Re: Kenwood KT-8300/9900 Tuner

rick.savas@...
 

Hi Joe,

I am pretty sure it is not a pulse count detector, but what is a multicative type of detector I am unsure of. I do know that I measured the thd on my unit a while back, I think I measured around 0.04% and some of that, maybe the source as I used a HP 8656B with an external oscillator.
I found on my KT-8300 it was not very selective for the tight grouping of stations in my area. I noticed some channel ghosting as well but we all know these issues can be specific to a unit &/or a location.
I went searching the net, I did find a page on using ltspice to create a FM modulated source which is cool but does not answer the question of how the multicative detector works
https://www.allaboutcircuits.com/textbook/radio-frequency-analysis-design/radio-frequency-demodulation/how-to-demodulate-an-fm-waveform/
Hopefully someone else knows know it works as it is the only tuner I can recall that uses that type.
Rick


Kenwood KT-8300/9900 Tuner

Joseph Strickland
 

I have a question for the group. Is the Kenwood KT-8300/9900 FM IF Detector (W02-0005-05) a Pulse Count Detector? The description in the service manual and the commentaries on the Tuner Information Center do not say just what kind of detector it is. It only says that it is a multicative detector (whatever that is). It is a rectangular black box on the circuit board.

So far the KT-9900  I acquired recently is the quietest tuner I have ever tried at my location. Alternate channel selectivity is better than many I have tried even in its FM Wide bandwidth mode. It is a real pleasure to use.

Joe


Re: Denon tuners

Joseph Strickland
 

John;

Great suggestion! We all know what can happen when batteries leak. Keeping the battery off of the circuit board will preserve the often delicate circuit traces.

Joe

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