Manual service tuner Onkyo Integra T-4970

[Florynsv]

Salut si sarbatori fericite! Are cineva din intamplare manualul de service de la tunerul Onkyo Integra T-4970? Pe net il gasesc doar pe site-uri care cer bani. Multumesc

[dan-a2]

https://www.radiomuseum.org/r/onkyo_integra_t_4970.html

 

Poate va ajuta cineva sa o descarcati de aici !!

[leoncris]

Onkyo T-4970
Believed to have been sold only in Germany, the T-4970 is thought to be identical to the T-488F except for voltage and tuning increments. Here's our contributor Lukas's great review: "I bought mine a few years ago on eBay Germany for less than 180 Euros, it was the silver version of that tuner and I was interested in it because of the DYNAS (=dynamic selectivity) feature it has. In a 1992 issue of the German hifi magazine Stereoplay was a detailed report about this tuner which explained this gadget. I hope I can translate the essence of this article although I am not an electrical engineer. The Dynas ciruit was developed by Telefunken as far as I know for use in car stereo equipment and provides a very narrow but variable IF filter: In a mixing stage the IF is set from original 10.7 MHz to 0.7 MHz. The very narrow variable bandwidths of the filters of the DYNAS IC are controlled by the audio signal. The louder the signal, the wider the filters. This works best in mono mode, so the most narrow filters are used only when the tuner works in mono mode. The Dynas option comes in addition to the conventional Wide/Narrow/Supernarrow settings known from the top of the line model T-9090/T-9990. But the Supernarrow is wider than with the 9090. According to Petsuya Toyama, tuner designer at Onkyo, the T-4970 is basically a cost-reduced T-9090 with a simplified IF section but added DYNAS and RDS capabilities. The Stereoplay report rated the 4970 in the same highest class as the 9090. You have to know that the tuner ratings in this magazine were based more or less solely on the DXing capabilities of the tuners. So the point was how many stations a tuner was able to pull in in the Stuttgart region, Germany. This of course is a very specialized situation and living in a different region would make you happier myabe with a different tuner because RF interference is not a problem and the audio quality might be more of an issue to you.

So what can be said about my sample? Well, it has a problem with the DYNAS circuit, bad news. Good news: I do not need it, there is no one single station where it could prove useful since the RF band is not really crowded here in Vienna, Austria (the problem should also be fixed easily, there is either a bad capacitor (styroflex type) or a bad PB connection with this capacitor, I will figure this out soon). When compared to my newly adjusted Yamaha T-2 it is a bit more sensitive. On some very weak stations it produces less noise, but the difference is very small and I have to say that a station that the T-2 can't pull in won't give you much of a listening pleasure with the T-4970, either. Sonically I can't complain, I have the impression of a smooth and warm-sounding tuner. However, I use it in my secondary system with homemade speakers which lack a bit of resolution in the mids and highs, and a rating under these conditions does not make much sense. So when you look for a tuner which should be able to seperate adjacent stations, go for it but have a look that the DYNAS circuit really works."

Lukas adds, "There are 6 filters in the IF section but I am unable to figure out how many of them are active in the different IF modes. The most straightforward guess is a 2+2+2 configuration for Wide-Narrow-Supernarrow. This is also one of the major differences to the T-9090, which employs a separate IF stage for each IF mode (as I was told). Although the service manual describes the procedure of aligning the DYNAS circuit, it is, at least for me, not very clear what to do. But maybe this is also a result of the defective curcuit, as the alignment procedure does not result in the demanded values."

Our contributor Nick adds, "I also have a silver-fronted Onkyo T-4970, bought via German eBay in December 2006. It was the second T-4970 I bought - the first one I bought in October of that year also had problems with the DYNAS circuit. Most of the time it would produce unintelligible audio at very low levels and with no stereo. Thankfully, DYNAS works fine on this one, although I find the response to be asymmetric, with better selectivity below a strong signal than above (the latter causes the audio to cut in and out as the DYNAS can't lock onto the weak signal). Perhaps this is just a matter of alignment. I find the audio to be very good, with a relaxed, smooth and natural sound, although my system isn't high-end. I preferred the sound to my previous tuner, a Sony ST-SA3ES. The Onkyo is a superb DXer, with great sensitivity and selectivity, although my Sony XDR-F1HD is the king of the DXers here."

https://www.electronica-pt.com/esquema/audio/onkyo-audio/onkyo-t-488-f-38803/

[Vizitator]

Am decat schema, daca te ajuta:

 

Onkyo_T4970_001.pdf

Onkyo_T4970_002.pdf

Onkyo_T4970_003.pdf

Onkyo_T4970_004.pdf

[Florynsv]

Multumesc tuturor pentru contributie, in special domnului leoncris, ala este!