Date   

Re: Sony fm tuner st a6b

sedond
 

hi dave,

if this is the one you bought, you may be s.o.l.:

https://www.ebay.com/itm/293529538093

while it would have been nice if the seller stated the tuning band, in the pics it's clearly visible that it's 76-90mhz.  not sure how canceling this sale would work out...

good luck,

doug s.

On Sat, May 9, 2020 at 05:50 PM, sedond wrote:

hi dave,

sounds like you got scammed - it's certainly a japan-spec tuna.  were there no close-up pics of this tuner?  i'd love to see a link to the ad.

i'd cancel your payment, and send it back - if the seller wants to pay for return shipping. (hopefully, you *did* pay via paypal and/or credit card.)

good luck,

doug s.


Sony fm tuner st a6b

sedond
 
Edited

hi dave,

sounds like you got scammed - it's certainly a japan-spec tuna.  were there no close-up pics of this tuner?  i'd love to see a link to the ad.

i'd cancel your payment, and send it back - if the seller wants to pay for return shipping. (hopefully, you *did* pay via paypal and/or credit card.)

good luck,

doug s.

On Sat, May 9, 2020 at 12:51 AM, exactadave wrote:
Sony fm tuner   st a6b   is an fm tuner from the 70’s and just got one off ebay……....really nice spec accept for the tuning dial………….the specs state the fm tuning range is normal  89.    To 108  aprox.   The dial that this tuna has is 75-91 mghtz……….can anyone help explain…………thanks dave.   I don’t bother you people very often but this is a confusion to me.    Thanks   dave


Re: Harman-Kardon F500 FM Tuner Restoration

tune in
 

Dave,

If you're looking to receive the full US FM band you'll need a different tuner. Ebay's return policy should allow you to send it back if you decide that tuner won't meet your needs. 

Tom



Sent from my U.S.Cellular© Smartphone


-------- Original message --------
From: "exactadave via groups.io" <EXACTADAVE@...>
Date: 5/9/20 11:20 AM (GMT-06:00)
To: FMtuners@groups.io
Subject: Re: [FMtuners] Harman-Kardon F500 FM Tuner Restoration

Yo know………..thank you very much………..will let the group know what I find out………….thanks again…..dave

 

Sent from Mail for Windows 10

 

From: tune in
Sent: Saturday, May 9, 2020 6:09 AM
To: FMtuners@groups.io
Subject: Re: [FMtuners] Harman-Kardon F500 FM Tuner Restoration

 

Dave, that tuner appears to be manufactured for the Japanese market and  most likely runs on 100 volts AC.  Check the information on the back of the tuner.  You will need a step up or down transformer for most countries outside of Japan and will only be able to access the lower end of the FM band (to 91mhz).

 

Tom

 

 

 

Sent from my U.S.Cellular© Smartphone

 

 

-------- Original message --------

From: "exactadave via groups.io" <EXACTADAVE@...>

Date: 5/8/20 11:51 PM (GMT-06:00)

To: FMtuners@groups.io

Subject: Re: [FMtuners] Harman-Kardon F500 FM Tuner Restoration

 

Sony fm tuner   st a6b   is an fm tuner from the 70’s and just got one off ebay……....really nice spec accept for the tuning dial………….the specs state the fm tuning range is normal  89.    To 108  aprox.   The dial that this tuna has is 75-91 mghtz……….can anyone help explain…………thanks dave.   I don’t bother you people very often but this is a confusion to me.    Thanks   dave

 

Sent from Mail for Windows 10

 

From: newaag via groups.io
Sent: Monday, May 4, 2020 8:16 PM
To: FMtuners@groups.io
Subject: Re: [FMtuners] Harman-Kardon F500 FM Tuner Restoration

 

On Mon, May 4, 2020 at 03:00 PM, Joseph Strickland wrote:

Do we know if more of the boards for the LM4500 will become available?


I'll let you know, I may try a new supplier, should be a month or two most. The one I used was closed until things got better.
Bob

 

 


Re: Harman-Kardon F500 FM Tuner Restoration

exactadave <EXACTADAVE@...>
 

Yo know………..thank you very much………..will let the group know what I find out………….thanks again…..dave

 

Sent from Mail for Windows 10

 

From: tune in
Sent: Saturday, May 9, 2020 6:09 AM
To: FMtuners@groups.io
Subject: Re: [FMtuners] Harman-Kardon F500 FM Tuner Restoration

 

Dave, that tuner appears to be manufactured for the Japanese market and  most likely runs on 100 volts AC.  Check the information on the back of the tuner.  You will need a step up or down transformer for most countries outside of Japan and will only be able to access the lower end of the FM band (to 91mhz).

 

Tom

 

 

 

Sent from my U.S.Cellular© Smartphone

 

 

-------- Original message --------

From: "exactadave via groups.io" <EXACTADAVE@...>

Date: 5/8/20 11:51 PM (GMT-06:00)

To: FMtuners@groups.io

Subject: Re: [FMtuners] Harman-Kardon F500 FM Tuner Restoration

 

Sony fm tuner   st a6b   is an fm tuner from the 70’s and just got one off ebay……....really nice spec accept for the tuning dial………….the specs state the fm tuning range is normal  89.    To 108  aprox.   The dial that this tuna has is 75-91 mghtz……….can anyone help explain…………thanks dave.   I don’t bother you people very often but this is a confusion to me.    Thanks   dave

 

Sent from Mail for Windows 10

 

From: newaag via groups.io
Sent: Monday, May 4, 2020 8:16 PM
To: FMtuners@groups.io
Subject: Re: [FMtuners] Harman-Kardon F500 FM Tuner Restoration

 

On Mon, May 4, 2020 at 03:00 PM, Joseph Strickland wrote:

Do we know if more of the boards for the LM4500 will become available?


I'll let you know, I may try a new supplier, should be a month or two most. The one I used was closed until things got better.
Bob

 

 


Re: Harman-Kardon F500 FM Tuner Restoration

tune in
 

Dave, that tuner appears to be manufactured for the Japanese market and  most likely runs on 100 volts AC.  Check the information on the back of the tuner.  You will need a step up or down transformer for most countries outside of Japan and will only be able to access the lower end of the FM band (to 91mhz).

Tom



Sent from my U.S.Cellular© Smartphone


-------- Original message --------
From: "exactadave via groups.io" <EXACTADAVE@...>
Date: 5/8/20 11:51 PM (GMT-06:00)
To: FMtuners@groups.io
Subject: Re: [FMtuners] Harman-Kardon F500 FM Tuner Restoration

Sony fm tuner   st a6b   is an fm tuner from the 70’s and just got one off ebay……....really nice spec accept for the tuning dial………….the specs state the fm tuning range is normal  89.    To 108  aprox.   The dial that this tuna has is 75-91 mghtz……….can anyone help explain…………thanks dave.   I don’t bother you people very often but this is a confusion to me.    Thanks   dave

 

Sent from Mail for Windows 10

 

From: newaag via groups.io
Sent: Monday, May 4, 2020 8:16 PM
To: FMtuners@groups.io
Subject: Re: [FMtuners] Harman-Kardon F500 FM Tuner Restoration

 

On Mon, May 4, 2020 at 03:00 PM, Joseph Strickland wrote:

Do we know if more of the boards for the LM4500 will become available?


I'll let you know, I may try a new supplier, should be a month or two most. The one I used was closed until things got better.
Bob

 


Re: Harman-Kardon F500 FM Tuner Restoration

Eric Benson
 

The Sony STA6B is the Japanese FM bandwidth version; check power too; you will need a 110v 50Hz to 120v 60Hz converter.  Your stations will be limited to only the lower range of US FM airwaves.


On Fri, May 8, 2020, 11:51 PM exactadave via groups.io <EXACTADAVE=AOL.COM@groups.io> wrote:

Sony fm tuner   st a6b   is an fm tuner from the 70’s and just got one off ebay……....really nice spec accept for the tuning dial………….the specs state the fm tuning range is normal  89.    To 108  aprox.   The dial that this tuna has is 75-91 mghtz……….can anyone help explain…………thanks dave.   I don’t bother you people very often but this is a confusion to me.    Thanks   dave

 

Sent from Mail for Windows 10

 

From: newaag via groups.io
Sent: Monday, May 4, 2020 8:16 PM
To: FMtuners@groups.io
Subject: Re: [FMtuners] Harman-Kardon F500 FM Tuner Restoration

 

On Mon, May 4, 2020 at 03:00 PM, Joseph Strickland wrote:

Do we know if more of the boards for the LM4500 will become available?


I'll let you know, I may try a new supplier, should be a month or two most. The one I used was closed until things got better.
Bob

 


Sony ST ST-A6b

John Carpanini
 

Hi,
 From your description of the tuning range, it appears that you have a unit that was intended for the Japanese domestic market.  If you look at the back the voltage requirements should indicate 100 Volts if I am correct.

JohnC
 


Re: Harman-Kardon F500 FM Tuner Restoration

exactadave <EXACTADAVE@...>
 

Sony fm tuner   st a6b   is an fm tuner from the 70’s and just got one off ebay……....really nice spec accept for the tuning dial………….the specs state the fm tuning range is normal  89.    To 108  aprox.   The dial that this tuna has is 75-91 mghtz……….can anyone help explain…………thanks dave.   I don’t bother you people very often but this is a confusion to me.    Thanks   dave

 

Sent from Mail for Windows 10

 

From: newaag via groups.io
Sent: Monday, May 4, 2020 8:16 PM
To: FMtuners@groups.io
Subject: Re: [FMtuners] Harman-Kardon F500 FM Tuner Restoration

 

On Mon, May 4, 2020 at 03:00 PM, Joseph Strickland wrote:

Do we know if more of the boards for the LM4500 will become available?


I'll let you know, I may try a new supplier, should be a month or two most. The one I used was closed until things got better.
Bob

 


Re: Replacing NiCd battery in Sanyo Plus Series T 55 tuner

hifigeezer
 

First the good news:

Another Batteries Plus Bulbs location was able to make up a new one for me.  They, like Bob, said the originals are 2/3 AA.  Unlike conventional batteries, these NiCads have rather flat positive terminals.

I measured the new battery and got 3.6 volts.  I installed it in the tuner and brought it up on a Variac just in case.

Now the bad news:

The memory function did not start working.  The tuner has six momentary ALPS switches, one selects a programmed station by pressing one of them in.  One of them seems to be stuck in the in position.

I did some listening and left it plugged in for a few nights, then installed it on a switched outlet.  The tuning no longer functioned at all!  Turning the knob produced no change.  Alas, 108.0 is not my favorite.

Powered it down and removed the battery; the tuning knob worked again.  The memory was programming not working, as one would expect.  Reinstalled the new battery, tuning knob still works, memory program not working :-).

Those six switches are not easily accessible without more disassembly.  As long as I can go from 89.5 to 91.5, I won't bother.

I suspect this unit has problems with the tuning circuit independent of the battery.  I may up selling it as a parts/repair unit.  If it continues to function, I will try to write a detailed report on the sound.  KBAQ, the IBOC station from hell, does need the narrow IF, as does the Pioneer TX-9500 II and Marantz ST 6000.  That station has IBOC problems on lots of good tuners.

Thanks to all for your help!


Re: Post Detection Filter with buffer

Radu Bogdan Dicher
 

Here's more work on this. 

Group delay measurements enclosed. Mind, you, again, these and not sims, but actual measured values (I assume, for instance, the notches can never go as deep as the sims show in actual measurement, as much as the GD measurements will be lesser than the ideal simulation of the circuit). By sims measures, this circuit (LTSpice file enclosed for anyone interested in tinkering with the circuit) and the original/Ray's are extremely close in group delay behavior, as shown before (BTW, if anyone's willing to lend me their built "Ray Post Detection Filter," I'd be happy to run measurements and make it more apples to apples). 

That said, I think if this one gets' some focused attention in the 70-100kHz range (and I'm excitedly looking forward to feedback from the group) it will be a very beneficial kit given its better frequency response (-3dB @ about 95kHz) and better potential integration in existing tuners/receivers. Very flat GD response all the way to 70kHz, and so in the 23-53kHz range all things are well if that's what really matters. 

An important point, for me, is that one of the further steps here is also employing higher Q inductors - the reason I kicked off that conversation over common mode chokes. I want to get some and try them out with this, though selection of parts to run through the gamut is a bit challenging at this stage. 

Radu. 

On Mon, May 4, 2020 at 5:02 PM Radu Bogdan Dicher via groups.io <vondicher=gmail.com@groups.io> wrote:
Bob,
Thank you for your feedback and points. I'm looking forward to further tweaking this design. 
I enclose what I'm getting from LTSpice for both circuits. This includes levels and group delay on the same plots. I also include a magnified view on the roughly 23-53kHz band. 
Radu. 

On Mon, May 4, 2020 at 4:22 PM newaag via groups.io <newaag=yahoo.com@groups.io> wrote:
here's the 19/38 notch filter simulation and board. On this design, passive de-emphasis was included in the response, hence the constant down slope. 
https://groups.io/g/FMtuners/files/LM4500%20Filter%20and%20buffer

I can likely find the notch simulation for the version without de-emphasis on my computer somewhere. 2 or 3 windows OS versions ago. 
As you can probably figure out, the higher the Q of the components used, the more narrow and deeper the notch is. But the more narrow and deeper the notch is, the harder it is to tune and get on exact frequency.
Bob


Re: TU-X1 - MODIFIED BY JOSEPH CHOW OF AUDIO HORIZONS [ME TOO!]

Paul
 

Not to say it was the case with this particular individual, but I know of other that as demand increased, this other company started to add staff that was lower cost and less qualified...to setup a bit of a factory floor to handle more units at the same time under the recognized name. Yet the true expert didn't even have time to review the work before it was sent back to the owner. So this one I'm thinking of went from a 1 person shop to a 4 person shop without disclosure and the quality suffered. The case I'm referring to goes back a few years when Mod shops were popping up everywhere on the web especially for CD player & DAC modifications... adding tube output stages and such. FM tuner modifications has never really flourished. Most shops that knew how to do alignments never ventured into modifications because the costs were too high in labor. And many have since sold their test gear and retired. I knew of one that was really a car head unit repair center for the big brands (because the CD portion or the tape portion would need repairing) but even that stopped as head units have really changed and became more disposable than repairable. So he closed because the repair part shrank so much he could not stay open just with FM alignments.


Re: TU-X1 - MODIFIED BY JOSEPH CHOW OF AUDIO HORIZONS [ME TOO!]

newaag
 

Please remember, all these repair techs are not like a manufacturer's repair center. They are mostly single individuals that, mostly, have been doing this for a long time.
It is important that we try to stay informed, based on feedback from group members, how these folks are performing. We will adjust recommended techs at TIC accordingly.
I guess some folks "loose their touch", or, whatever, and have a hard time saying no to new business. Even though they probably should.
We advise everyone to be careful with any job involving large $ rebuilds or repairs.  
Bob


Mitsubishi DA-F20 Alignment

newaag
 

I wanted to start a new thread related to this topic, especially while it is fresh on my mind. Lest I forget...
It will get post it here as I can, in sections with pics. Then probably posted on TIC on the DA-F20 review assembled as a pdf or something.

To start, lets talk about the very important Detector adjustments that someone with a DC voltmeter / multimeter can do. The easy stuff.
Then also address the stereo VCO adjustment, which also is quite simple and easy, but can completely disable a tuner from stereo if it's off kilter.
Bon Voyage!
Bob 


locked Re: Measuring and matching 10.7 MHz ceramic filters

newaag
 

On Wed, May 6, 2020 at 08:39 PM, Radu Bogdan Dicher wrote:
I'm invariably getting about 5dB lower readings on the left/lower side of the response plot. I'm definitely willing to persist quite a lot, but I'd really love to figure out where the deficiency is...
Give it a break, and come back to it after a couple days. If your unit might be defective, maybe look at the limit for returns pronto tonto.
It would be useful if you filled in the blanks in the middle data area. Use the mouse to place the cursor in the plot area. Put the cursor in the middle of the filter response and click to move the cursor there. This will add data to the cursor 1 field. And that data will show numbers for ESR, L, C, impedance, phase, gain, etc derived from both S11 and S21 that can be used to help determine what is different in your fixture, cal, or hardware / firmware nanoVNA, as indicated in your plots. 
OTOH, this current plot looks better than all previous ones.
There appears to be an odd noisy effect just below 10.7 MHz that hardly shows on the upper response curve, but is jarring on the group delay plot. Oddly, it also corresponds to a deep notch in the left side filter response at the bottom, that may be related to the broad lower left side pull down. I cannot explain it.  
You will be really glad you bought that HP54522A Scope when I show you more tricks you can do with it to measure the IF Path in tuners, and raw filters. It will give you an alternate path to verify all this stuff, including filter response. and tuner IF filter response.
In the mean time, feed the nanoVNA CH0 into the 54522A. Below 300 MHz you will see a nice square wave with a 600 ps risetime. This guy can cause resonance problems with all that upper frequency energy being pumped out.  
Bob


Re: Rotel RT-1084 Help Needed

daschwa79
 

Adding an update and some pictures.  I took out the tuner module(broke some things along the way) and removed the shields.

The tuner board has a top and bottom, pictures are attached and labeled as such.  The coils are on the top.

After I put it back together I tweaked some coils and eventually got it to where my preferred station would come in quickly in HD.  The coil on the lower left of the board seemed to increase volume of the analog singal.  The coil on the upper right (Red circle) seemd to effect ability to lock in HD reception.  All stations still show one bar in Analog mode.  This was a very unscientific process (obviously without test equipment)

I'm pretty certain this thing is seriously out of alignment or has a bad part somewhere, or both.   Without a service manual not sure of a way forward but as my preferred station is working could use this as an HD tuner for a spare room.

My hopeful side thinks this thing could still be salvaged.  Any further ideas from the experts appreciated.

Dave



locked Re: Measuring and matching 10.7 MHz ceramic filters

Radu Bogdan Dicher
 

After recalibrating - which I'm about to redo, as I'm not 100% sure of all steps - I'm getting this out of a 150kHz filter (JA). I trust I need to recalibrate or maybe the device is subpar?... I'm invariably getting about 5dB lower readings on the left/lower side of the response plot. I'm definitely willing to persist quite a lot, but I'd really love to figure out where the deficiency is...
Radu. 
image.png


On Wed, May 6, 2020 at 8:12 PM newaag via groups.io <newaag=yahoo.com@groups.io> wrote:
Here is a wider frequency scan showing, for comparison, the response of both the previous Murata 280 (red) and Murata 150 (black). Note, these are better examples of almost perfect looking filters. They don't all look this good, for frequency or shape. As one can see, the group delay gets very noisy outside the filter passband. 
Bob


locked Re: Measuring and matching 10.7 MHz ceramic filters

newaag
 

Here is a wider frequency scan showing, for comparison, the response of both the previous Murata 280 (red) and Murata 150 (black). Note, these are better examples of almost perfect looking filters. They don't all look this good, for frequency or shape. As one can see, the group delay gets very noisy outside the filter passband. 
Bob


Re: Need help with Mitsubishi DA-F20

newaag
 
Edited

I wanted to update this topic with more information. Here's a quick recap of the problem. The tuner, a DA-F20, did not play in stereo, and reception was poor.
A quick alignment showed the both detector zero adjustments were way off. The narrow detector on this unit is used to enable both muting, and also stereo reception. If that detector is not at zero, stereo will not engage, regardless of any other settings (muting off, etc). So this was a quick fix.
But there was more wrong - the reception sensitivity was poor, and distortion measured high.
It turned out the crystal oscillator was off specification, (as per previous messages), tuning the IF to 10.67 instead of 10.70. It appears the previous tech who worked on this unit also saw this, and tried to correct it, but installed the wrong ceramic filter set in narrow (4 filters). They were marked, in handwriting, 10.72 on each filter, so they were obviously tested and sorted before installation. But the correction went the wrong way - 10.67 filters should have been used.  
It was likely an easy mistake to make, though. I frequently do a very low RF signal test, in IF narrow. Then tune the RF signal generator slightly above and below the station frequency (say 98.10 MHz), to see if noise goes lower and sensitivity improves slightly off frequency. It is a good test for crystal oscillator based tuners. 
For this tuner, initially the sensitivity improved, with lower noise, with the stereo generator tuned about 30 kHz above the actual target station - in this example, it was best at 98.13 MHz. 
This could give one the impression that the IF filters need to be moved "up" in frequency from 10.70. In fact, if the actual IF is measured, it would be where the oscillator told it to be, at 10.67. This is due to frequency inversion, as noted in previous messages. But...
The "fix" may not be using new narrow filters selected for 10.67 MHz. Because one needs to measure the other IF (wide) IF path, and see where it is "centered". In this case it was measured, and found to be correct, at 10.70 MHz. When going to all this trouble, you want the IF path centers to "match" each other, AND also match the oscillator. And in this tuner, the wide LC filter is a closed box and non-adjustable. So the wide IF drives which filters you select for narrow, and where you adjust the crystal oscillator.
Long story short - a new 10.000 MHz crystal was installed, and the 20 pf cap was selected so it ran exactly on frequency. Then 4 new narrow filters were fitted, all selected for 10.700 MHz. 
Then the tuner was completely re-aligned - this is a MUST after moving the IF frequency (from 10.67 to 10.70) and fitting new filters.
These changes completely transformed the tuner - it now is both sensitive, selective, and tests very low for distortion in both wide and narrow, with excellent stereo separation (over 50 dB in both wide and narrow).
That is basically the end of the story. I will document the alignment "how to" specifics elsewhere at a later time. The service manual could be a lot better for this unit.
Bob


Re: TU-X1 - MODIFIED BY JOSEPH CHOW OF AUDIO HORIZONS [ME TOO!]

sedond
 

well, it's been a lot of years since i've used joseph chow's services, and i had very good results.  15 years ago, he converted a japan-spec acuphase t109 for me, and upgraded it as well.  the work was very good.  a couple years later, i had him convert a japan-spec sansui tu-x1 for me, he also upgraded it.  again, i was pleased with the work.  in fact, a couple years later, when i started hearing audible crackling noises in the audio output, i sent it back to him, and he replaced aging caps that were causing the noise.  i was only out the shipping costs to get it back to him.  no, i did not have him go through the entire tuner, replacing everything the 1st time around - i can only imagine what it would cost to do that to a tuner like the tu-x1.

perhaps his efforts have diminished more recently?  i would suggest reaching out to him directly with any issues you may have had.  in my experience, he always tried to make things right.

ymmv,

doug s.

On Tue, May 5, 2020 at 12:42 PM, Mark Hubbard wrote:
Unfortunately, I too have had negative experiences with Mr. Chow's work. A few years ago he sold me a modified Music Hall mmf-25 CD player, supposedly having upgraded parts and enabling it to be used as a digital transport with an external DAC as well as a stand-alone CD player. As a CD player, it worked for a while and then lost output to the right channel. I took off the cover and noticed a small component that he added had become unsoldered at one end. A local repair shop was recently able to resolder the joint for me at a cost of $50, but when I try to use the mmf-25 as a transport, it doesn't work at all. Add to that the difficulty I had getting the unit in the first place (requiring threatening him with a bad review on Audiogon before he finally shipped it to me), and I too cannot recommend his "upgrades." I'm only out about $400 altogether, and the CD player works as such, but I would not buy equipment or services from him again. Your mileage may vary.


locked Re: Measuring and matching 10.7 MHz ceramic filters

newaag
 

For comparison, here is the same filter. Blue plot is the standard response. The black lower plot shows the effect of adding a 180 pf C to the output (instead of 10 pf).
Insertion loss goes way up (response goes down)
Bob

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