Since I've had this Kenwood KR6030, I have replaced quite a few parts and that was due in no small way to help from this forum. All parts were to do with power amplifier, power supply and control boards. Last night I was happy with the end result and buttoned up the top and bottom covers. Once done, I thought to give it another listen. Listening was through headphones with a Discman plugged into AUX. All was good.
Then I switched input to TUNER and nothing. It is dead. No stations, no static, no response at all from signal strength or center tune meters.
This was totally unexpected because when I obtained the receiver in September, the tuner was working. I even remarked to myself about how well it picked up both of the available local FM staions with nothing for an antenna.
The only thing I have imagined that's preventing the tuner from operating is that it's somehow been deprived of power. I have just finished measuring voltages at both ends of the wires feeding the tuner from the power supply and am seeing 26V and (-)26V. So power is getting to the board.
Can anyone suggest where I might look for a cause as to why the tuner no longer works?
FWIW, I did nothing at all to the tuner circuitry. Everything I did was elsewhere within the receiver.
Then I switched input to TUNER and nothing. It is dead. No stations, no static, no response at all from signal strength or center tune meters.
This was totally unexpected because when I obtained the receiver in September, the tuner was working. I even remarked to myself about how well it picked up both of the available local FM staions with nothing for an antenna.
The only thing I have imagined that's preventing the tuner from operating is that it's somehow been deprived of power. I have just finished measuring voltages at both ends of the wires feeding the tuner from the power supply and am seeing 26V and (-)26V. So power is getting to the board.
Can anyone suggest where I might look for a cause as to why the tuner no longer works?
FWIW, I did nothing at all to the tuner circuitry. Everything I did was elsewhere within the receiver.
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Is it muted due to no signal or is there an odd voltage within the AM/FM oscillators.
Follow the service manual voltage/oscillator paths.
Have you tuning voltage.
Are the selector switch contacts in good condition.
If both AM and FM are not working, that points to a supply issue.
Follow the service manual voltage/oscillator paths.
Have you tuning voltage.
Are the selector switch contacts in good condition.
If both AM and FM are not working, that points to a supply issue.
Thank you for responding.
Yes, neither AM or FM are working.
This is the only proceedure in your suggested steps that I feel somewhat confident in performing. The input selector switch is composed of wafers that are individually removeable according to the service manual. I will do this to examine the contacts with the hope that the problem is solved by cleaning them.
Can you please identify where I can measure voltage(s) to see if they are odd?
I am not very adept at following schematics so unsure which voltage figures I should test for.
I have never delved into a tuner before so tuning voltage is something else I do not know where to check for.
If it helps, below is the schematic section containing the AM and FM oscillators.
As usual, I spoke too soon apparently.
The illustration in the service manual depicts removing input selector switch wafers but gives no detail. It looks straight forward beginning with pulling out the switch's shaft.
But it does not pull out or perhaps does not pull out easily. I can see nothing in the way of a clip or fastener at the other end that needs to come off.
So far I have tried pulling from the splined end of the shaft and gentle tapping at the other end with a punch and hammer. But so far the shaft has not budged. I did not want to be too forceful for fear of breaking some part(s) of the switch.
Should I get more aggressive or am I missing something that keeps the shaft from sliding out?
I got the impression from step 3, "unsoldering it's feet" that the wafers could be removed individually without unsoldering them all and removing the entire switch assembly.
The illustration in the service manual depicts removing input selector switch wafers but gives no detail. It looks straight forward beginning with pulling out the switch's shaft.
But it does not pull out or perhaps does not pull out easily. I can see nothing in the way of a clip or fastener at the other end that needs to come off.
So far I have tried pulling from the splined end of the shaft and gentle tapping at the other end with a punch and hammer. But so far the shaft has not budged. I did not want to be too forceful for fear of breaking some part(s) of the switch.
Should I get more aggressive or am I missing something that keeps the shaft from sliding out?
I got the impression from step 3, "unsoldering it's feet" that the wafers could be removed individually without unsoldering them all and removing the entire switch assembly.
Looking closely at the photo I posted of splined end of the tuner shaft, I noticed what could be a circular clip and it was. After removing it I expected to be able to pull the shaft completely out but I cannot. It will now slide back and forth 1/4" or so but not all the way out.
I'm stymied.
Should I grip it with pliers and pull hard or tap harder than I did before at the other end with hammer and punch?
Has anyone disassembled one of these Kenwood input source selector switches?
It's become frustrating. Especially so because I thought taking it apart for a cleaning would be easy - something I could manage. And it may or may not even be the cause of the dead tuner.
I'm stymied.
Should I grip it with pliers and pull hard or tap harder than I did before at the other end with hammer and punch?
Has anyone disassembled one of these Kenwood input source selector switches?
It's become frustrating. Especially so because I thought taking it apart for a cleaning would be easy - something I could manage. And it may or may not even be the cause of the dead tuner.
Well I am an idiot for sure....real slow on the uptake.
It did not occur to me until this morning that the input selector shaft might be pulled out by extracting it from the rear.
With that mystery solved, I can begin unsoldering the switch wafers to clean the contacts. Maybe even solve the dead tuner problem.
It did not occur to me until this morning that the input selector shaft might be pulled out by extracting it from the rear.
With that mystery solved, I can begin unsoldering the switch wafers to clean the contacts. Maybe even solve the dead tuner problem.
Kind of hard to believe that the oxidized wafers can silence a source completely.
I would suspect something more simple going on...
I believe you and I am going to abandon removing the wafers of that switch because I think I found the problem.
In addition to the +/-26V going to the tuner, I found another wirw that's supposed to be conducting 14V. But I measured 0V. That led me to invstigate regulator transistor Q1. There is supposed to be 50V present at Q1 collector which there is but that 14V is supposed to eminate for Q1 emitter. But no voltage is there. I have to think that Q1 is faulty.
Graphics on the face or Q1 say D620. I searched 2SD620 and found really nothing. The service manual cites Q1 as either a 2SC789 or 2SD526 so I opted to search for "2SC789 replacement". Right at the top was a link to a DIY Audio thread form someone looking to replace that same regulator transistor in a Kenwood KR5030. One model below the KR6030 that I have.
Of the several transistors tossed around as replacement candidates, a TIP41C got a couple of nods and I have some of those from a previous project.
Tomorrow I will do that swap and, fingers crossed, there will be tuner again.
EDIT: After comparing the specs of a 2SC789 transistor with a TIP41C transistor I see that my proposed TIP41C replacment has an hFE of MIN 20 whereas a 2SC789 has an hFE of MIN 40.
Will that be problematic?
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It turned out the transistor at Q1 was not to blame for no power going to the tuner. The problem was one of the new capacitors I installed in the power supply. I learned this after being coaxed into examining the area around Q1.
Polarity of all the new caps I installed was correct.
After removing the power supply, in preparation for a Q1 transistor swap, it was suggested that I inspect what components there were surrounding it. One solder join of a new capacitor did not look quite right so I re-flowed it and that was the problem.
The tuner was restored to functionalithy.
Polarity of all the new caps I installed was correct.
After removing the power supply, in preparation for a Q1 transistor swap, it was suggested that I inspect what components there were surrounding it. One solder join of a new capacitor did not look quite right so I re-flowed it and that was the problem.
The tuner was restored to functionalithy.
Good news
Btw I have a kr-5030, the power switch is toasted. Not sure if the kr-6030 is the same but if it is then you might want to consider installing a relay to replace the use of the switch which would only be used to run the 110v Ac relay coil. I just did this on a old akai am-2800 which has the same issue of worn out contacts that were welded together. I had to take the old switch apart to unweld the contacts but the switch is now working fine only supplying a small amount of current,mA to energize the relay coil. Digi-Key has a chassis mount relay that I used. I’ve seen others use a triac as well
Btw I have a kr-5030, the power switch is toasted. Not sure if the kr-6030 is the same but if it is then you might want to consider installing a relay to replace the use of the switch which would only be used to run the 110v Ac relay coil. I just did this on a old akai am-2800 which has the same issue of worn out contacts that were welded together. I had to take the old switch apart to unweld the contacts but the switch is now working fine only supplying a small amount of current,mA to energize the relay coil. Digi-Key has a chassis mount relay that I used. I’ve seen others use a triac as well
Yes, the power switch in this KR6030 was problematic. I learned that very shortly after acquiring this receiver in September when searching for gerneral info. It had the "flickering dial lights" symptom.
A thread that I read on AK described cleaning the switch and installing a triac. I opted for triac as opposed to relay simply due to cost and a more simplified installation.
Once removed and opened up, the switch was heavily coated internally with carbon and the switch contact points (double contact points wired in paralell) were dark and pitted. I spent a fair bit of time cleaning those points without using sandpaper or a file. The ponts cleaned up nicely I thought and with the triac in place, dial lamp flicker was gone.