Hi everyone ! I have found an otl philips amp for sale with the matching philips speakers. The seller tells me that he picked that up from an old console that had 6 speakers into it, 3 left and 3 right. He is asking 50 canadian bucks for the lot. Is it cheap enough for me to give it a try ? I’ve read good reviews about this setup when the speakers are working.
Edit : It actually isn’t an otl amp from what i’ve found on the internet. I could find pictures of the inside of the amp and there are OPTs. The amp has a 12AX7 driving the tone control, and two ecl86 in the power stage.
Edit : It actually isn’t an otl amp from what i’ve found on the internet. I could find pictures of the inside of the amp and there are OPTs. The amp has a 12AX7 driving the tone control, and two ecl86 in the power stage.
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Yes, I've been thinking that this can't be an stereo OTL amp at all, as four output tubes were needed and only two ones are depicted. And these two tubes by no way look like EL86's/6CW5's.
Btw: Are your ECL86's good? They have become rather scarce and expensive these days 😎.
Best regards!
I see you edited the post, so 50 bucks is too much, sorry - I thought it was an OTL amp...
Agreed. It's mediocre at best and doesn't even feature that hum cancellation design that was so common with SE amplifiers in radios of those days.
Best regards!
Best regards!
I thought that it might have been an otl because of the speakers in the first place. They made the same speakers with an 800 ohm impedance. When I dug deeper into the philips otl I realized that two tubes were missing.
I haven’t put the ECL86s on the tester. They look like they have lost their vaccum (top are clear ish, no more silvery like they are supposed to be). The EZ81 is still good, the 12AX7 seems weak, but I yet have to get used to my tester, wich is an eico 667. I’ve never seen a tube go all the way in the "good" section of the meter. I have two good ECL86s on hand for when i’m done testing the amp and removing the useless parts in it, like the tuner. I’ll put new caps in the PSU before plugging it into the wall.
Could you elaborate more on that ?
Too late, already bought it. I don’t think it’s too bad of a deal considering all the parts and speakers that I got with it. The seller even gave me a nice heathkit adjustable resistor Also, philips OTLs can only drive 800 ohm speakers, wich is not very useful. The amp was running recently so It might only need a few things to get back on the road. Tube parts are scarce in my area, so even if it’s not the deal of the century, i am not disappointed either.
Btw, I picked up an old Dumont scope for 20$ in the same run. It’s full of 12au7, has a nice 10h choke and the PT is interesting too.
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If the ECL86's that came with your device were good, your expenses were justified by some extent…😱
Best regards!
Best regards!
The 6GW8 availability issue can be dealt with by switching to PCL86 stock and coping with the heater voltage difference. At least for now, PCL86 stock can be sourced. Look here.
IMO, of particular concern is C50, an instance of the notorious "Death cap.". Modernization to employ a proper, 3 wire, safety grounded, power cable is strongly suggested.
IMO, of particular concern is C50, an instance of the notorious "Death cap.". Modernization to employ a proper, 3 wire, safety grounded, power cable is strongly suggested.
I was concerned about this cap too. Should I remove everything on the primary side of the PT and rebuild that in a more modern way ? all the circuits are grounded to the chassis, and at multiple places. Is there anything else that could cause any risks of getting shocked or to set the whole thing in fire ?
Also, I thought of converting the amp to use one 12AX7 as the drivers and two EL84s for the output. Both tubes are still in production and I have many of them on hand. I’ve read that the ECL86 is more or less 1/2 12AX7 with an el84 in the same envelope. I also read that they don’t sound the same, but I like the EL84 sound...
Also, I thought of converting the amp to use one 12AX7 as the drivers and two EL84s for the output. Both tubes are still in production and I have many of them on hand. I’ve read that the ECL86 is more or less 1/2 12AX7 with an el84 in the same envelope. I also read that they don’t sound the same, but I like the EL84 sound...
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The power Pentode within the ECL86 is a BPT version of the good old EL41 with the same data. But as the EL84 datasheets usually contain operating points for a plate dissipation of 9 watts, you might apply these as well.
Does the power transformer cope with the much higher heater current?
Best regards!
Does the power transformer cope with the much higher heater current?
Best regards!
I don’t have any idea of the PT ratings, but I think that after removing the tuner circuit wich contain 4 tubes, it will definitely be enough to drive a 12ax7 and two el84s, even if I keep the tone stack.
Before committing resources to this project, be sure to check if the power transformer does mechanically hum under load. This was common on cheap tube radios. I would also remove the end bells to inspect the insulation of the wires. The bells need to be stripped and repainted anyway.
Good idea, I’ll verify that. And regarding the investment into the projet, my first objective was to make it work as it is now in order to do some tests. If it needs to much work I wont put any more time into it.
I might need your help with that. I removed everything related to the tuner section, and also got rid of the input switch. I don’t need all this stuff and want to keep only the amp and the tone stack since they are on the same pcb. But, the wire in red in the picture went from the pcb to the input selector switch, wich isn’t there anymore. I see that it’s related to the tone stack, but I don’t know if it’s still useful or not. From what I understand, the two caps that connect to this wire would be used only with one particular input, probably the phono. The amp had different filters that could be used with the phono input, depending on the kind of record that was played. Would it be ok to just remove those wires without affecting the functionality of the tone stack ?
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Forget it. It works flawlessly. At least for a bench test 😀
I’ve put new ecl86 in it, a three prong power cable, a fuse holder and a switch. It didn’t need anything else than that. The original caps seems to hold up to this point (they won’t stay for long anyway...) there is no excessive hum or noise at this point, using alligator clips for the speakers
I’ve put new ecl86 in it, a three prong power cable, a fuse holder and a switch. It didn’t need anything else than that. The original caps seems to hold up to this point (they won’t stay for long anyway...) there is no excessive hum or noise at this point, using alligator clips for the speakers
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