Hi All. I have the 5500 Mk2 tuner that works perfectly and sounds good, but every "locked" station shows a frequency of +0.05MHz. QUESTION, is this just a case of the frequency counter of the display needing a fine adjustment or does more complex adjustment need to be done? I realise it would benefit from a total accurate realignment, but cannot find anyone in the UK that can do it. If it is just the frequency counter how do I adjust this please? .....Thanks for reading.
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There is no adjustment in the service manual for this. These tuners actually lock and measure the local oscillator and assume a 10.7 MHz IF. The IF frequency is fixed by the ceramic filters.
I suspect the 4.5 MHz crystal X501, used by the PLL MCU IC501 has drifted off a little with age (1984 model!). Fixing this is quite involved - buying crystals as specials is not easy these days, so if possible just live with it.
I suspect the 4.5 MHz crystal X501, used by the PLL MCU IC501 has drifted off a little with age (1984 model!). Fixing this is quite involved - buying crystals as specials is not easy these days, so if possible just live with it.
Usually it's just the discriminator alignment that needs a tweak in this situation. Very common. Adjust L204 and L202 as described in the service manual on a real station while tuned to its nominal frequency, that should work just about as well as a signal generator. If in doubt, grab another PLL-synthesized FM receiver of conventional, no-frills construction and tune in its LO signal at tuned frequency + 10.7 MHz for a cross-check.
I have tried a number of PLL-synthesized shortwave portables in my possession, and none have disagreed by more than a few hundred Hz on FM, so actual reference oscillator inaccuracy wouldn't be high on my list of possible causes.
I have tried a number of PLL-synthesized shortwave portables in my possession, and none have disagreed by more than a few hundred Hz on FM, so actual reference oscillator inaccuracy wouldn't be high on my list of possible causes.
There should also be a difference in de-emphasis, 50 us for Europe, 75 us for the United States, but that has no relation to the problem.
Unless you have accurate calibration equipment, it will be a tedious project, it is not so big a problem.
A precision cut crystal from a specialist will cost more than 200 US Dollars, maybe more. They are used by companies having set channels, like taxi services, and when ordered in bulk, the price goes down.
I would live with the problem, the equipment to do the RF alignment is expensive.
A precision cut crystal from a specialist will cost more than 200 US Dollars, maybe more. They are used by companies having set channels, like taxi services, and when ordered in bulk, the price goes down.
I would live with the problem, the equipment to do the RF alignment is expensive.
I would change all the electrolytics in the RF section , clean the section of dust, tobacco residue etc., and check voltages at IC section before and after capacitor replacement.
A small pF across supply rails would be added.
A scope to check noise on supply rails would give some idea if noise is an issue, and see if the mains supply needs new electrolytics.
Dry joints were common in some Sansui sets, no idea about Hitachi.
That is if you want to something, these are precaution against future failures.
A small pF across supply rails would be added.
A scope to check noise on supply rails would give some idea if noise is an issue, and see if the mains supply needs new electrolytics.
Dry joints were common in some Sansui sets, no idea about Hitachi.
That is if you want to something, these are precaution against future failures.
Very many thanks to everyone for all your replies. From all of them, the one fix suggested, by sgrossklass, looks like the only one that I have any confidence in actually doing. It also has several acknowledgments by other members, so maybe I will be brave enough to try this at some time. I agree I could just ignore and leave it as it is but it is just such a very nice tuner, and little things like this bug me. (slightly). Obviously if I spoil it in some ways, I am going to regret it immensely. Perhaps I will mark the cores of the coil so I can return them to the current position if things go wrong Thanks again
The MK2 service manual details how to align the detector coil. This and the stereo decoder PLLs are the only coils you should touch without RF test equipment. Do NOT touch the tuner head section.
Even marking the tuning slug is not perfect as it may be very brittle and may be glued.
The manual seems to show a single sided PCB, so it solder joints will be very fragile
Even marking the tuning slug is not perfect as it may be very brittle and may be glued.
The manual seems to show a single sided PCB, so it solder joints will be very fragile
I have now decided to leave it alone David. I think I stand a good chance of breaking it. If I can find a REAL expert tuner alignment service, I might let them have a go. I have to say, I have forgotten so much about how these tuners work. I did know 45 years ago but not now, so I'm not confident about playing around with it. I still ultimately would like it completely realigned though. Thanks for your warnings...
The real problem is obsessive guys like us AND the fact they gave us two decimal places on the display to fuel latent OCD tendencies! Plenty of tuners will lock 50kHz low when scanning up and lock 'correctly' when scanning down. Or vice-versa. And then you've got some tuners with 'fine tuning' down to 10kHz steps...
Yes John, I'm definitely one of those sadly!. Sometimes I call myself a perfectionist, other times I think I'm just a big worrier. Maybe they are all descriptions for the same mind set. Bottom line is that if I can see something is absolutely not right, it ticks away inside my brain and won't go away.... ever! PS: I did get the Kenwood tuner working OK (if you remember you helped) What was wrong I didn't really find out. I ended up tapping it and it stayed on working. I continued to try to find faulty soldering but there was none evident. Whether I DID anything to fix it permanently I just do not know. Only time will tell
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