Philips 794 Receiver?

[boreas]

I just picked one up today and I can't really find anything on it. To complicate things, there is apparently another 794 receiver which I saw referenced online but it looks quite different from the one I picked up.

This particular one was made by Philips when they had a manufacturing facility in Illinois, so this is a Made In The USA Philips which is kind of cool. Looking at this thing, it appears to have somewhere between 15 and 25 WPC and is pretty short on features. It even has a "Common" connection for both left and right speaker grounds.

Frankly, I don't really know why I bought it other than to satisfy my curiosity and maybe broaden my knowledge.

I haven't listened to it yet except through headphones. The switches and pots are quite dirty and I'm out of DeoxIT. Also the DC offset for the right channel is really unstable, swinging from somewhere around +90 to out of range on the - side. I can stabilize it by jiggling the input selector switch so maybe the DeoxIT will fix it.

Anyone know anything about this or about other US built Philips gear?

Thanks,
John

 

[ryuuoh]

It's a handsome looking little guy. Give it a clean up when you have the stuff, then see where you stand.

 

[boreas]

It's a handsome looking little guy. Give it a clean up when you have the stuff, then see where you stand.

I'll pick up some DeoxIT tomorrow but, in the meantime, I worked the heck out of the controls dry and the DC offset's stable and within spec. It's around 9 mV left and 11.5 right. Not bad.

Apparently the "Philips High Fidelity Laboratories" line, which this comes from, contained some pretty nice gear. I guess we'll see whether this receiver is part of the good stuff.

John

 

[vintageboy]

I am curious how it will sound, I have never heard Phillips receiver or amp

 

[boreas]

I am curious how it will sound, I have never heard Phillips receiver or amp

Me too.

Me either.

John

 

[reggaenaut]

Vintage Philips is well regarded on this site, but I am not up to speed on the particular models. A very knowledgable Aker is Brian: I hope he is able to chime in.

 

[mhardy6647]

Should be good.

sorry these are sideways
This is as close as I can get - the 784 and 7841 (silver and black, respectively)

http://www.audiokarma.org/forums/showthread.php?t=55218

FWIW, one of its younger, cheaper brothers passed through here a while back...
(looks like the model number is 7800)

 

[boreas]

Should be good.

sorry these are sideways
This is as close as I can get - the 784 and 7841 (silver and black, respectively)

Thanks. That gives me a better perspective. It looks like the AH784 was from a different series but, according to Orion, produced during the same period, (1977-1981) as the AH794. Odd.

Their ranking within their respective series is indicated by the last digit in the model number. What Orion indicates is that the AH784 and AH794 would be BOTL. Both had 20 WPC into 8 Ohms. The AH785 and AH795 were next at 30 WPC, then the AH786 and AH796 at 45 and then the AH787 and AH797 at 60 which seems to be the TOTL.

I Googled the TOTL AH796 and came up with this AK thread from Brian. He seems to like it.

A Few more photos. As noted previously, the receiver has a common ground post for both the left and right sides. I think this promises to be sort of a PITA so I made up a couple of pigtails out of bullet and fork connectors and a length of zip cord. That should simplify things.

John

 

[boreas]

The switch & pot cleaning did the trick. DC offset is stable at -10.8 mV left and -12.9 mV right. I hooked it up to a pair of KLH Seventeens and it sounds really good, a lot of presence and enough power to put good clean bass out of the KLHs.

Nice little receiver!

John

 

[68custom]

I bought on of those 794s when new in 77/78 as I remember, it was black and I thought it was cool. well it looked cool, but if you looked at it long it would blow an output, matter of the fact if you turned it on it would blow an output. but it did look good, sold for 20$ repaired, under warranty, and felt lucky to have sold it at all. did sound good when it did work though.

 

[boreas]

I bought on of those 794s when new in 77/78 as I remember, it was black and I thought it was cool.

That would make it a 7941.

well it looked cool, but if you looked at it long it would blow an output, matter of the fact if you turned it on it would blow an output. but it did look good, sold for 20$ repaired, under warranty, and felt lucky to have sold it at all. did sound good when it did work though.

It does sound nice, especially considering the wattage. As for the outputs, these appear to be the originals so I suspect the problem you had wasn't universal or even particularly common.

John

 

[Oilmaster]

Nice unit, but I never knew that Philips had a factory in the USA ! Notably because I'm from nearby Philips' hometown Eindhoven in Holland, with plenty of friends and neighbours working in Philips' factories at the time. In Europe, most of such equipment would be built in Holland until they closed the hifi gear factories and moved them to Singapore after 1980. It seems that Philips did have a dedicated factory for North America. Hmmm...

Anyway, when you search for information on any Philips gear, always put the prefix '22'.

Like that, you will easily find a free service manual.... (http://www.eserviceinfo.com/index.php?what=search2&searchstring=22AH796) (if you are not familiar with it, make sure you download all parts by clicking on the 0,1,2,3 by 'multipart' in the next window).

Some recommendations: the OPS emitter resistors are often underrated in Philips gear from that era. Check carefully the surfaces off all power resistors for cracks and the like, and replace them with 1 or 2 watt higher rated resistors. All caps are more or less still in production; the original Philips capacitor factory was sold to BC, then Vishay bought BC. Up to today, some Vishay BC capacitors still carry the original Philips coding (and blue colored).

I haven't check out the schematic myself, but in that era Philips often had output stages which were running in pure class A for the first 10 watt (and therefore the heatsink can be slightly warm at lower output volume). Like the entire tone control part, which was definitely not a classical Baxandal circuit, but rather a cascade of separate tone control stages with a class A buffer stage at the end of each tone control. Very particular, but it had that typical clear and transparant Philips sound.

 

[Oilmaster]

Some recommendations: the OPS emitter resistors are often underrated in Philips gear from that era. Check carefully the surfaces off all power resistors for cracks and the like, and replace them with 1 or 2 watt higher rated resistors.

Well, looking at your pics again, this thing doesn't have (anymore) the typical Philips standard carbon cylindrical resistors, but the square cemented emitter resistors. I'm not sure if they are original, considering the space they occupy, above other components. Perhaps you can see on the solder side if any component has ever been replaced. The bended transistors are a typical sign of a repair technician going through the circuit for fault searching.... Some repairs might actually be beneficial.

...

 

[Oilmaster]

Having some Philips gear myself, I couldn't help to download the service manual and study it with the end-of-the-day beer

This is definitely one of those typical Philips circuits.... lovely.

Firts of all, being a typical Philips amp of that era, this is not a DC coupled amplifier, meaning that there is only a positive power rail and mandatory coupling capacitors between each stage, including between the power output stage and speakers. As such, DC offset is not a topic related to this amplifier, neither you can adjust it. If there is any DC on the speaker terminals, it means that you are measuring the leakage current through the output capacitors. The value is not alarming, though replacement with quality caps could give some sound improvement (and protect your speakers).

The quitest current is to be set at ................. 75 mA. this means the typical Philips design that the amp runs (for a part) in pure Class A. :yes:

The output caps may give you a typical 'hump' at switch on/off.

Two other nice design surprises:

- the headphones are not 'tapped' from the output stage.... no, it's directly coupled at the output of the tone control (pre-amp). When you plug in the headphones, the output stage is disconnected from the pre-amp stage. This is directly in your sonic benefit, because the pre-amp is biased in pure class A in full range and no additional distortion is added by the OPS stage!! But of course, due to the single power rail, a coupling cap is in between, and replacing this one with a quality one (e.g. Elna Cerafine) might do a lot of good. This design is not often seen.

- an additional output from the pre-amp (at the entry of the OPS stage) is made for a connector to Philips' MFB (motional feedback system) speaker system (an active speaker system, very sought after in Europe, google for mfbfreaks)

Anyway, if you don't want to keep the tuner, I would definitely strip the pre-amp and power amp board and build a very nice class A headphone/power amp system. Perhaps the PCB and built doesn't look impressive, but the circuity actually is. And replace all components in that case of course, it's an ultimate project candidate....

 

[boreas]

Nice unit, but I never knew that Philips had a factory in the USA !

It's reasonable to suppose that the Philips factory (factories?) in the US were old Magnavox factories that Philips acquired through the purchase of Magnavox.

Anyway, when you search for information on any Philips gear, always put the prefix '22'.

Yes, I stumbled onto that fact. In this case you have a suffix to deal with. Mine is a 22AH794/44. There is a European model, a 22AH794/00, which is quite different.

Like that, you will easily find a free service manual.... (http://www.eserviceinfo.com/index.php?what=search2&searchstring=22AH796) (if you are not familiar with it, make sure you download all parts by clicking on the 0,1,2,3 by 'multipart' in the next window).

Thank you! Quite a useful site.

Some recommendations: the OPS emitter resistors are often underrated in Philips gear from that era. Check carefully the surfaces off all power resistors for cracks and the like, and replace them with 1 or 2 watt higher rated resistors. All caps are more or less still in production; the original Philips capacitor factory was sold to BC, then Vishay bought BC. Up to today, some Vishay BC capacitors still carry the original Philips coding (and blue colored).

Thanks again. I'll check those resistors this evening.

I haven't check out the schematic myself, but in that era Philips often had output stages which were running in pure class A for the first 10 watt (and therefore the heatsink can be slightly warm at lower output volume). Like the entire tone control part, which was definitely not a classical Baxandal circuit, but rather a cascade of separate tone control stages with a class A buffer stage at the end of each tone control. Very particular, but it had that typical clear and transparant Philips sound.

John

 

[VINTAGCHRIS]

nice looking piece, a buddy of mine has one of those from that series, its either that one or the one below it, i remember the sound being very clear and powerful for the smaller size of the transformer his had, i gave it a good deox for him as like yours it had developed static in the switches.

growing up one of my friends dad was a phillips dealer before they pulled there products from the US leaving him high and dry, i remember he had some fantastic higher power total model phillips units as well as a pair of there larger speakers, it was quite impressive and it would be a good many years before i heard anything equal to it.

 

[boreas]

Having some Philips gear myself, I couldn't help to download the service manual and study it with the end-of-the-day beer

This is definitely one of those typical Philips circuits.... lovely.

The site in your link doesn't seem to have the service manual for this unit. Your link was for the 22AH796. When I typed in both 22AH794 and 22AH794/44 nothing came up.

John

 

[Oilmaster]

The site in your link doesn't seem to have the service manual for this unit. Your link was for the 22AH796. When I typed in both 22AH794 and 22AH794/44 nothing came up.

John

Hi John,

Oops, you're right, it's the 796... they made too many close-numbered models. I did a deeper search around, but no luck so far for a free 794 manual , I'll look further.... also because there is one put up for sale for 10 euro here (tuner part not working). I can only find paid manuals for the moment. I wonder how close (or not) the 796 and 794 actually are.

 

[TAGO MAGO]

growing up one of my friends dad was a phillips dealer before they pulled there products from the US leaving him high and dry, i remember he had some fantastic higher power total model phillips units as well as a pair of there larger speakers, it was quite impressive and it would be a good many years before i heard anything equal to it.

I am not surprised Philips pulled the plug on their US stereo components since I don't think, at least the receivers, sold particularly well. Not that there was anything wrong with them, but by 1979, the majority were going for Pioneer, Technics and Sony leaving other brands like Philips, Nikko and even, to a certain extent, Sansui in their shadow. I blame a certain lack of advertising compared to top selling three.

 

[boreas]

Hi John,

Oops, you're right, it's the 796... they made too many close-numbered models. I did a deeper search around, but no luck so far for a free 794 manual , I'll look further.... also because there is one put up for sale for 10 euro here (tuner part not working). I can only find paid manuals for the moment. I wonder how close (or not) the 796 and 794 actually are.

I think finding a SM for this receiver is going to be complicated by the fact that the Netherlands and the US factories built entirely different models with the same designation. For instance, my receiver has 20 WPC and the other 22AH794 is rated at 60 WPC "Music Power" (40 WPC "Sine Wave" - RMS?? - DIN??). It looks quite different as well.

So, while the home market 796 (your link) may be similar to the home market 794, the home market 796 will likely be worlds different from the US 794. I think the only SMs likely to be of use are the ones for the US line.

22AH794/90 (Holland)

22AH794/44 (US)

John