Kenwood KT-1100 - diyAudio
Go Back   Home > Forums > Source & Line > Analogue Source

Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 5th November 2007, 07:38 PM   #1
stex is offline stex  Serbia
diyAudio Member
 
Join Date: Jun 2004
Location: Paracin Serbia
Default Kenwood KT-1100

Frequency counter did not display correct value, when listen to station over 104MHz, eg station 106.2MHz, display 89.3 or something similar. I donít have service manual or schematics, please help.
  Reply With Quote
Old 12th September 2012, 11:19 AM   #2
diyAudio Member
 
Join Date: Mar 2004
Location: Krakow
Default another question

Hi
I renewed this thread because I do not want to start a new thread.
I bought Kenwood ST-1100 and started mod it.
Please look at the schematic of analogue output filter and amp.
I want to remove C94,100 (short).
before those caps is 0V.
What do you think, is it safe to make shorts? Maybe those caps are the part of High Pass Filter?
Is there a danger to appear DC after shorting?
Attached Images
File Type: jpg kt1100out.jpg (57.5 KB, 108 views)
__________________
regards, Pawel
  Reply With Quote
Old 12th September 2012, 12:26 PM   #3
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
They are safe to short out and do not form any part of the filter circuits. Just confirm afterwards that there really is 0.00 volts DC at pin 7 of the final opamp. Even if there is a slight voltage (say less than 20mv) it is not necessarily a problem as most preamp inputs are AC coupled anyway.

You might find replacing the opamp with a FET type reduces the offset to zero as long as the input (R98) is AC coupled (in the part of the circuit not shown) or has a true 0.00 volt DC on it anyway. For something like this it could well be an upgrade too.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 12th September 2012, 12:30 PM   #4
diyAudio Member
 
Join Date: Mar 2004
Location: Krakow
Quote:
Originally Posted by Mooly View Post
They are safe to short out and do not form any part of the filter circuits. Just confirm afterwards that there really is 0.00 volts DC at pin 7 of the final opamp. Even if there is a slight voltage (say less than 20mv) it is not necessarily a problem as most preamp inputs are AC coupled anyway.

You might find replacing the opamp with a FET type reduces the offset to zero as long as the input (R98) is AC coupled (in the part of the circuit not shown) or has a true 0.00 volt DC on it anyway. For something like this it could well be an upgrade too.
thank you Mooly,
I am going to change IC12, IC9 to better ones
and use jfets instead of IC10,11 in the filter.
this means C94 will remain (but better quality, probably Panasonic), C100 will be shorted
__________________
regards, Pawel
  Reply With Quote
Old 12th September 2012, 12:33 PM   #5
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
That sounds like a plan and modern electroylitics aren't all bad you know. I would be happy with modern quality 100uf electroylitics fitted here.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 13th September 2012, 08:24 AM   #6
diyAudio Member
 
Join Date: Mar 2004
Location: Krakow
the first thing I moded was supply of the opamps from the section of filters.
I soldered the caps from the pins 4,8 and connected them to local central point of the ground.
I expected better trebles
but
got heavier bass and the sound was "more quiet" with "consistency"
Attached Images
File Type: jpg 2012-09-13-114.jpg (99.0 KB, 90 views)
__________________
regards, Pawel
  Reply With Quote
Old 13th September 2012, 08:36 AM   #7
diyAudio Member
 
Join Date: Mar 2004
Location: Krakow
then
I shorted C99/100 and paralleled C93/94 with paper in oil caps 10u/160V.
like before expected nicer trebles
and
I heard beautifull voices the midrange is extraordinary!
wow, that was it
the conclusion is that smearing trebles is because weak quality opamps and they will be changed/ecluded with jfets during next mod.
Attached Images
File Type: jpg 2012-09-13-117.jpg (511.0 KB, 92 views)
__________________
regards, Pawel
  Reply With Quote
Old 13th September 2012, 09:42 AM   #8
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Decoupling opamps isn't always straightforward.

If there is noise on the rails and you decouple to ground... then you inject that noise into the ground system. If that is used for signal purposes then you see the problem.

Sometimes just decoupling rail to rail can be best. It kills the noise and doesn't contaminate the grounds. I've also come to accept the view that a small cap and low value non inductive series resistor (say 2 ohm or thereabouts) can be the best compromise.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 13th September 2012, 09:55 AM   #9
diyAudio Member
 
Join Date: Mar 2004
Location: Krakow
Quote:
Originally Posted by Mooly View Post
Decoupling opamps isn't always straightforward.

If there is noise on the rails and you decouple to ground... then you inject that noise into the ground system. If that is used for signal purposes then you see the problem.

Sometimes just decoupling rail to rail can be best. It kills the noise and doesn't contaminate the grounds. I've also come to accept the view that a small cap and low value non inductive series resistor (say 2 ohm or thereabouts) can be the best compromise.

anyway I decoupled rail to rail too, do you see a cap between the paper in oil caps?
but I will try to remove decouplers to the ground and check if the sound will be better?
because now is excellent
thank you for the comments
__________________
regards, Pawel
  Reply With Quote
Old 13th September 2012, 10:36 AM   #10
diyAudio Member
 
east electronics's Avatar
 
Join Date: Jan 2006
Location: Athens GREECE
Decoupling modifications and especially with exotic parts can hardly be done afterwords IE the return to ground in such a complicated ( from design aspect) machine might have weird opposite or bad results .

Additions like the ones that you are trying to perform can be done either on a design stage or in equipment that is far less complicated inside . Use of exotic and often microphonic parts has way to many variables and there is a chance that will have worst results .Often one smd ceramic multilayer placed down under the OP amp will have better results than your approach ...you may as well try that.

It is very optimistic to think that op amps are drop in replaced Often OPAMPS with astronomical speed will require different compensation methods or circuits ( eventhough pins are compatible ) In cases like that oscillation is around the corner waiting for you .

Finally to be honest with you machines like the one shown eventhough from circuit aspect might perform many zeros when it comes to THD estimations but in real life the PCB and the structure of the machine will compromise and consume most of these zeros and make your mods worthless and most of all not cost effective .

That of course mainly applies to amplifiers ...audio section of tuners will be easier still the same rules apply ...

kind regards
sakis
__________________
SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Acoustat 1+1 from Spectra 1100? noelm Planars & Exotics 2 19th February 2007 06:52 PM
FS: Parasound PLD-1100 pjanda1 Swap Meet 2 27th August 2005 08:52 PM
nokia 1100 nbcd Digital Source 4 14th March 2005 08:31 PM
Mullard QY4-400/1100 on ebay uk bigparsnip Swap Meet 0 18th March 2004 12:24 PM


New To Site? Need Help?

All times are GMT. The time now is 05:08 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2