Pioneer RT-707 Capacitor Upgrade and Service

Great Job Trevor. Your thread will serve as a useful guide for many others.

As for the 'refurbished' you see in some sales, it seems like people use that term even when they deoxit the a couple of pots or clean the RCA outputs.

Live with your machine for a while, and pay attention to any teething over coming weeks. And if all works out, get back in touch after a while when you do your annual service! :)
 
Great Job Trevor. Your thread will serve as a useful guide for many others.

As for the 'refurbished' you see in some sales, it seems like people use that term even when they deoxit the a couple of pots or clean the RCA outputs.

Live with your machine for a while, and pay attention to any teething over coming weeks. And if all works out, get back in touch after a while when you do your annual service! :)

Thanks very much mate. And a very BIG thank you for all your input and advice, and of course your original thread that gave me the confidence to have a go at this myself.

Cheers!
 
Thanks very much mate. And a very BIG thank you for all your input and advice, and of course your original thread that gave me the confidence to have a go at this myself.

Cheers!

A large factor in many of these 707 threads moving forwards instead of getting stuck as tricky points is GPS. :thumbsup:
 
Hi all,

As I begin to enjoy my 'new' RT-707 I am thinking about the future life of the heads. A little while ago I was lucky enough to pick up a full head block that had come from a working machine. These heads seem to be in quite good condition, although of course they have some wear. Probably no worse than the heads in my machine, and possibly better.

Here are a few pictures of this second hand head block.
Unfortunately it is very difficult to photograph these things, and get good contrast and clarity.
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I have been thinking about sending these off to JRF Magnetics, but before following that up I was wondering just what the best approach is going to be regarding the removal/replacement of heads on the 707.

As you can see from the images these heads have all their wiring still intact and in good condition (except where they have been cut :)). I expect that I will need to de-solder the wiring from the second hand set anyway before sending them to JRF Magnetics.

But on their return I was contemplating fitting some 4 pin Mini Molex connectors, one for each head, into the loom inside the 707 and also on each set of head wires, and then being able to simply unplug the original heads and plug in the replacements. Although I suspect this would be pointless as once the 'new' heads were fitted and setup on the machine I would not be swapping them out.

So, just how careful do you need to be when soldering around Magnetic Heads? I would imagine that too much heat would be a bad thing for the fine coils in the heads? Have any of you ever replaced heads in an R2R machine? I guess any system would do here, not just an RT-707.

Cheers.

PS: I am not imminently planning to change my heads. Just looking into the future.
 
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Trevor - You may want to check with John French since I believe he can accept the head block assembly as it is and remove, lap, re-mount and optically align the heads so that only minimal adjustments would be required at your end. This would allow you to pull and replace the head block as an assembly rather than having to remove, install and fully align the individual heads.
 
Hi Trevor,

Personally I would keep the wiring As Is. The plugs and sockets in the wiring to heads should be kept to a minimum as they become breaks in screening which will let hum and noise in, we are talking high amp gains here!! I suspect that the wires from the heads are Twin Screened cable with the screen grounded at the PCB. This shield should not be breached.

I have replaced a few heads but these have been on Revox machines. This has been mainly to change configuration from 2 Track to 4 Track. I have yet to have troubles which were due to soldering.

I would make enquiries about leaving it as a item too. The heads can then be put in the same physical position following lapping. Should you wish to do so. I would leave them as they are if the wear is not heavy and the surface is not blemished apart from the wear pattern. You have an easy way to set the head height and the test tapes will set the azimuth spot on. I would pack them away nice and comfy and wait until the present heads are worn out. From my own machine which was used a lot, This took 25 Yrs plus!!!!

Thanks for the compliment earlier in the thread!!!

Enjoy your machine!!!

GPS16
 
Trevor - You may want to check with John French since I believe he can accept the head block assembly as it is and remove, lap, re-mount and optically align the heads so that only minimal adjustments would be required at your end. This would allow you to pull and replace the head block as an assembly rather than having to remove, install and fully align the individual heads.

Hi there mate,

Heavens, if I gave the impression I was going to dismount the heads from the head plate, then I apologise. That is the furthest thing from my mind. I was only thinking of removing the wiring, leaving the heads mounted as they are. It is hard to tell from the pictures above but this set of heads still has the Pioneer blue lacquer on all of the mounting and adjustment screws, so absolutely original Pioneer setup.

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Cheers.
 
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Hi Trevor,

Personally I would keep the wiring As Is. The plugs and sockets in the wiring to heads should be kept to a minimum as they become breaks in screening which will let hum and noise in, we are talking high amp gains here!! I suspect that the wires from the heads are Twin Screened cable with the screen grounded at the PCB. This shield should not be breached.

I have replaced a few heads but these have been on Revox machines. This has been mainly to change configuration from 2 Track to 4 Track. I have yet to have troubles which were due to soldering.

I would make enquiries about leaving it as a item too. The heads can then be put in the same physical position following lapping. Should you wish to do so. I would leave them as they are if the wear is not heavy and the surface is not blemished apart from the wear pattern. You have an easy way to set the head height and the test tapes will set the azimuth spot on. I would pack them away nice and comfy and wait until the present heads are worn out. From my own machine which was used a lot, This took 25 Yrs plus!!!!

Thanks for the compliment earlier in the thread!!!

Enjoy your machine!!!

GPS16

Hi GPS,

Thanks for your comments. Your point about not breaking the sheilding on the head wiring is well taken. That was in fact what was concerning me, hence my question.

This set of heads is generally in fantastic condition. Yes, the heads have some wear, but it is not bad, and is very even. As I think you can tell from the images above the wear channels are not deep, and the head faces themselves are very clean, smooth and shiny. Better in fact than the set of heads that are currently in my machine. I consider myself very lucky to have come across and picked up a complete mounted set like this.

So I shall do as you suggest and pack them away for a 'rainy' day.

I have however sent an e-mail to JRF Magnetics and attached these pictures which show the heads a little better. I shall be interested to hear back from JRF.
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Many Thanks,
Trevor
 
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Hi Trevor,

not heavy wear at all on them.

You should have seen mine when I let the machine go for spares!!!

Oh Well, I now have Revox machines and enjoy them very much. I hope you will do the same with your 707.

For a brief period, I used it as an alarm clock. The start of Time - Pink Floyd from Dark Side Of The Moon cannot be ignored!!!

Cheers.

GPS16
 
Hello again All,

I have been having a great time with my 'new' RT-707 over the past couple of weeks. I am really very impressed by its performance. When recording I cannot really pick any audible difference between the source material (Vinyl) and the recorded tape, apart of course for a little hiss that tape decks always add.

This brings me to my question for today. I have noticed that when playing back my recordings the level of hiss is slightly higher in the right channel. It's not extreme and certainly well below normal signal levels when listening to music, but in quiet passages between tracks I can pick that the right channels is noisier than the left.

If I was to try and isolate where the hiss is being generated, where should I look. Which areas of the electronics might cause this sort of behavior?. Alternatively, is this just a function of the way the heads work?

Cheers.
 
I agree with phantomrebel. I use DBX 224 units on all of my decks and hiss is a non-issue. When used with properly calibrated decks, these units produce incredibly quiet recordings.
 
Hi Trevor,

as you have a Millivolt meter at you disposal, try using the Scope probe with the probe set to X1 (if it is switchable). If you don't have a X1 probe use some screened lead with a Croc Clip on the end. I have had a croc clip on a long terminal screwdriver and used it as a probe on more than one occasion.

With the MIC pot down, as they will introduce hiss on their own. Go through the amps from start to finish logging the readings for both channels at the same places. If they seem to be OK then the Head amps may be the cause. They are high gain in the first place so will output some hiss anyway.

See where that points you. If you follow the circuits and home in on all the Electrolytics which are DC blockers. Just pick the side of the Cap where the DC isn't. If there is DC on both sides then put a 0.1uF cap on the end of your probe. You are looking for hiss so a 0.1uF should be OK.

Cheers.

GPS16
 
Trev,

Hiss should the same on both channels. If it isn't, there is either an issue with your ears/speakers/amp (does it swap when you swap L / R on your amp/speakers), or with the machine. But how big a difference are we talking about in mVrms? Some very small difference could be expected, but I would be surprised if you could hear the difference so I suspect a problem in r2r or amp/speaker/ears As GPS says, confirm by scope and let us know what you come up with

BTW I played some 7.5ips tapes at Burning AMP 2017. Amp after amp was rotated through this source/speaker combo (12" Tannoy HPO in a horn scenario). Volume was pretty much always just below clipping on whatever amp was being auditioned; hiss was really audible but I did record my tape a bit 'hot' - people were floored by the little Pioneer. At one stage someone tried to use a CD player and there was rumbling in the crowd and the r2r was reinserted after a two tracks. A highlight was having Nelson Pass' new preamp using my humble 707 as a source for much of the afternoon in this room.

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Have you thought about a noise reduction unit? Hiss is a thing of the past since I've been using dbx gear.

Hi mate,

Thanks for that tip. I have looked for a DBX 224 unit many times, but finding one that is set for 240V 50Hz can be a real challenge. All the units currently available are US, 117V 50/60Hz versions. I guess I could always use a step down transformer as the DBX 224 uses very little power.

Thanks.
 
Hi Trevor,

as you have a Millivolt meter at you disposal, try using the Scope probe with the probe set to X1 (if it is switchable). If you don't have a X1 probe use some screened lead with a Croc Clip on the end. I have had a croc clip on a long terminal screwdriver and used it as a probe on more than one occasion.

With the MIC pot down, as they will introduce hiss on their own. Go through the amps from start to finish logging the readings for both channels at the same places. If they seem to be OK then the Head amps may be the cause. They are high gain in the first place so will output some hiss anyway.

See where that points you. If you follow the circuits and home in on all the Electrolytics which are DC blockers. Just pick the side of the Cap where the DC isn't. If there is DC on both sides then put a 0.1uF cap on the end of your probe. You are looking for hiss so a 0.1uF should be OK.

Cheers.

GPS16

Thanks heaps for that GPS.

My Scope probes do have and X1 setting, so I could try what you have suggested. Although my skills in tracing circuitry and taking these sorts of measurements are less than limited.

I'll see how I go.

Cheers.
 
Trev,

Hiss should the same on both channels. If it isn't, there is either an issue with your ears/speakers/amp (does it swap when you swap L / R on your amp/speakers), or with the machine. But how big a difference are we talking about in mVrms? Some very small difference could be expected, but I would be surprised if you could hear the difference so I suspect a problem in r2r or amp/speaker/ears As GPS says, confirm by scope and let us know what you come up with

BTW I played some 7.5ips tapes at Burning AMP 2017. Amp after amp was rotated through this source/speaker combo (12" Tannoy HPO in a horn scenario). Volume was pretty much always just below clipping on whatever amp was being auditioned; hiss was really audible but I did record my tape a bit 'hot' - people were floored by the little Pioneer. At one stage someone tried to use a CD player and there was rumbling in the crowd and the r2r was reinserted after a two tracks. A highlight was having Nelson Pass' new preamp using my humble 707 as a source for much of the afternoon in this room.

Wow, that is impressve Smurf!

I just tried some simple tests based on your comments. I swapped the left and right RCA leads on the back of the 707. I then mounted a blank tape, set the Mic and Line input levels to zero (my Mic levels are always at zero) and started erasing the tape. To my amazement the slightly louder hiss still seemed to be on the right channel!!!!! (I would have expected it to move to the left) Now as this noise is not in evidence with any other input source, I'm pretty sure it is not the Amp, Speakers or Headphones, it only occurs when the 707 is playing a tape and I also suspect it is probably not the 707 either. I may have to get my ears checked :eek:

One good thing though is that the difference is very small, I can pick it, but the noise level is well below the signal level when playing any music, and I cannot sense any volume difference left to right in normal listening. I might even investigate trying to find a DBX 224.

Cheers mate.
 
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