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Kenwood KT 7500

Easy EMI Options at HiFiMART.com

sachu888

Well-Known Member
Joined
May 8, 2010
Messages
2,710
Points
113
Location
Gwalior,Nashik
I recently acquired this tuner, very very special thanks to FM and friend John K Antony:thumbsup: who carried this from US and again shipped it to me. I was searching for a high end tuner but cost and shipping was too much. I got it in a decent price from a Audiokarma member.
There is a big dent in left side of faceplate caused in shipping. I switched it on as soon as I open it, but only could listen it for a min and saw smoke on dial and panel and meter lights went off. I immediately called to Om for help and he advised to check few points
I opened top cover and saw one 47uf capacitor bulged and a resister burnt. Seller converted dial lamps to LED (AC to DC). Original tuner uses transformer secondary 27v with 27R resister to drop it to 24V Ac to power three 8W, 300ma lamps in series.The burnt cap and resister mounted on to the board which provides power to LEDs. On further checking I found one panel led was missing from original place and was touching something near mains power inside. I think that LED touched something in mains and got that cap and resister burnt.
I have now removed LEds and enjoying the good sound of Analog tuner. I am able to get Fm stations like Radio City, Big FM and Vibid bharti from Surat, Gujarat, without any antenna or special mod, only single small wire is used.
The signal strength is always full on all local stations. My Sony and another tuner used to get very low signal. The SQ is amazing.There is a vast improvement over my previous tuners.
FM Tuners had some very nice comments about the Kenwood Kt- 7500
No wonder - it has a 5 gang FM tuner.
According to them it can beats almost any highend tuner (with some cap and opamp upgrade) irrespective of price. I will later upgrade the cap and Opamp, and post here.
Now the sad part panel light is not working and a big dent on faceplate. I will correct it asap. Some pics:



















Sorry for the mobile pics.

Regards
Sachin
 
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Hiten

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Joined
Oct 17, 2008
Messages
2,686
Points
113
Location
Kalyan
That is a nice tuner Sachin. Congrats ! The reception you are getting without antenna speaks for itself.
See if you think this is ok. Put thick cloth or leather on both side of the face plate. Put thick metal strips on the cloth/leather, hold them with small vice or C clamp and slowly tighten it to see if face plate comes to normal position.
Regards.
 

analogadikt

Active Member
Joined
Feb 19, 2009
Messages
231
Points
43
Location
Navi Mumbai
Great score Sachin:)

The charm of a full analog tuner with a backlit dial and silver face is something special. FM Antony deserves appriciation for such a helpful geasture. Regarding that dent, am sure you can mend it. You can also use pieces of plywood covered with leather/rexine in a c clamp as suggested by Hiten.

Regards,
 
Joined
Aug 14, 2011
Messages
160
Points
18
Location
Karnal
Congrats Sachin for acquiring such a nice Analog Tuner. I am also a fan of such Tuners.
Cheers !
 
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sachu888

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Joined
May 8, 2010
Messages
2,710
Points
113
Location
Gwalior,Nashik
Update

My Kenwood has a De- Emphasis switch at back panel. User can select between 75us to 25us setting. 75us setting is meant for US only, and 25us intended for Dolby(now extincted). We require 50us de-emphasis for balanced sound. The sound quality was very bright with 25us setting. It was good with 75us but I knew it will further improve in 50us.
I had no option but to modify either one of the de emphasis switch. I contacted Omishra yesterday regarding the issue, and emailed him the service manual. He suggested to interchange the position of four Silver foil caps in the circuit. He suggested the excellent suggestion. I didn't have to bother about searching for new caps. The solution is below:

There were Cb47, Cb48 both 750pF along with 33K? and Cb89, Cb 90 - both 1500pF.Switch makes it either 750pf (for 25S) or 750+1500=2250 (75S)
Simple solution was to exchange positions of 750 pF with 1500 pf
Then I got 1500 pF (for 50S) or 1500+750= 2250 pF (for 75S)
By result I changed 25S -> 50S and 75S remains same.
I than de stock JRC opamp and installed an opamp socket. I first tried with Opa2134. It was very good. I listen it with half an hour and decided to try LM49720, and I settled with it.
Tuner is now sounding very balanced. I have not heard very expensive CD players,but this tuner sounds better than my other digital set up. I am not exaggerating at all. those who have similar kind of tuners can confirm this. I now have plan to fully mod this tuner suggested here Tuner Information Center - Jim and Bob's DIY Mods

FM De emphasis switch near power cord


Top cover removed


Bottom plate removed. You can see the underside of PCBs


Top view


Silver foil caps


Stock JRC Opamp


Removed stock opamp and socket installed


New Opamp installed


Regards
Sachin
 

manniraj

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Joined
Jun 3, 2011
Messages
2,601
Points
113
Location
Bangalore
Sachin the internals look as brand new from the pictures, I think a very good buy with the way the tuner has been maintained :clapping:
 

kuks1

Active Member
Joined
Feb 4, 2014
Messages
101
Points
28
Location
mumbai
even though most of what sachin said went over my head, i understand that the radio is souding nicer and thats what is important. You guys ( you sachin and omshira and others who make modifications i never thought were possible) are really crazy...i mean awesome:). enjoy the tuner and keep up the good work.
cheers!!!
 

sachu888

Well-Known Member
Joined
May 8, 2010
Messages
2,710
Points
113
Location
Gwalior,Nashik
Manniraj, there is no hint of dust even on outer parts. It's approx 40 year old tuner, but looks brand new.

Regards
Sachin
 

sachu888

Well-Known Member
Joined
May 8, 2010
Messages
2,710
Points
113
Location
Gwalior,Nashik
Changed lamps few days back. I got them from here http://www.dgwojo.com/index.php?p=1_2_Products
There are three bulbs in series, driven directly off the power transformer secondary AC winding, which is 29 VAC. This tuner uses a series 27 Ohm resistor to drop the voltage to 24 VAC, as 8 volt bulbs were used. I had some issue regarding voltage, due to incorrect reading by my DMM. I later confirmed this with Omishra and told me to go ahead. The Kenwood originally used bulds with Green cover. I got the same colour from the seller.
The result, sorry for mobile pics:










Regards
Sachin
 
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