Leak TL/12 Plus / Point One Plus
Radford Revival
Trade: Radford Revival
The Radford SC22 balance control works in the same way, weird!
brecklandboy
pfm Member
Ditto with the balance 'slider' on my Quad 22 pre-amp.
Tony L
Administrator
Interesting to know it is fairly typical for its era with regards to the balance control.
I’ve given the controls and valve bases a better clean and it is now working great. No crackle! It is much better and far more usable than I was expecting. It adds a bit more body and warmth over the passive, if less actual information/clarity; stereotypically ‘valve’ sonically, in a nice warm and easy-going way, but still funky and engaging. I’ll be curious to try the phono input at some stage, though that means lumping a lot of kit around, so it can wait.
I’ve given the controls and valve bases a better clean and it is now working great. No crackle! It is much better and far more usable than I was expecting. It adds a bit more body and warmth over the passive, if less actual information/clarity; stereotypically ‘valve’ sonically, in a nice warm and easy-going way, but still funky and engaging. I’ll be curious to try the phono input at some stage, though that means lumping a lot of kit around, so it can wait.
Tony L
Administrator
On closer listening there is a left/right character imbalance that I guess points to some resistor imbalance somewhere. It is both a tonal and punch thing and doesn’t seem to be valve related (I have lots of nice EF86s).
I’m not too bothered, my plan was only to ‘get it working‘, not to try and unseat my regular Audio Synthesis passive (which is just a wide-open window in comparison), but worth noting for anyone going down this route. I’m going to leave it alone. It is good enough (actually sounds great!), and it completes the set. A really nice thing to have.
If at some point in the future I stumble across another totally untouched mono Point One pre identical to the one I have (or even a pair of earlier metal-face Point Ones), I may be tempted to do a full strip and rebuild on the pair the way I did on the TL12 Plus power amps. That interests me rather more due to the additional phono stage EQ options. I don’t really want to rework this stereo one any further as someone had already been at it. I may go round again at some point with the meter and see if I can spot a huge imbalance left/right on a specific resistor pair, but I‘d already tried that and not found it.
I’m not too bothered, my plan was only to ‘get it working‘, not to try and unseat my regular Audio Synthesis passive (which is just a wide-open window in comparison), but worth noting for anyone going down this route. I’m going to leave it alone. It is good enough (actually sounds great!), and it completes the set. A really nice thing to have.
If at some point in the future I stumble across another totally untouched mono Point One pre identical to the one I have (or even a pair of earlier metal-face Point Ones), I may be tempted to do a full strip and rebuild on the pair the way I did on the TL12 Plus power amps. That interests me rather more due to the additional phono stage EQ options. I don’t really want to rework this stereo one any further as someone had already been at it. I may go round again at some point with the meter and see if I can spot a huge imbalance left/right on a specific resistor pair, but I‘d already tried that and not found it.
Barrymagrec
pfm Member
It`s possible that the moldseals round the tone controls that you didn`t replace are the cause of the imbalance, not a dangerous fault but affecting the frequency response.
Tony L
Administrator
That is certainly worth thinking about. Are they in circuit in the middle-point of the tone control ranges? I guess they must be. I know the ones I took out weren’t capacitors anymore!
IIRC there aren’t many of them (possibly only two), and the previous person hasn’t been near them so I’ll think about changing them. I’ve got some 0.01uF in stock (the yellow ones) so probably worth a go doing C16 L&R.
I think there are another pair on the rumble filter, though I assume they are out of circuit when disengaged?
Barrymagrec
pfm Member
I think the caps on the tone controls will affect things if they are short / open / leaky, the rumble filter caps probably not when not selected.
Tony L
Administrator
I got the cat to do it earlier:
Did the rumble-filter too. Fiddly, but a good learning experience.
The slight burn-mark on the orange wire near the rumble filter was neither the cat nor me! It was there previously, almost certainly done by whoever tried to put the far too big mustard caps in nearby. I’m actually tempted to replace the two largest as they really don’t fit!
One of the black Hunts caps on the treble pot just shattered into a load of plastic shards as soon as I went near it, so I suspect it had been broken for years and may well have been the problem. The others measured around 0.04-0.07uF on the Fluke. The Peak ESR meter wanted nothing to do with any of them. I have a feeling it can’t measure really low values, but they were clearly screwed so no need to overthink it. The fact one was likely not even in one piece was almost certainly the issue. It is certainly sounding better and more balanced now. I’d not say 100% compared to the precision I’m used to with the Audio Synthesis attenuator, but not obviously off anymore and it sounds very nice indeed.
I seem to have lost the light on the front. May just be loose, or I may have trashed the bulb filament fiddling around moving it. No big deal. I’m kind of tempted to leave it as I was a little worried about heat damaging the ancient printing, though it does look cool. That said I will be using the AS Passion long-term, I just wanted to get this working. I’ll test the bulb later. I potentially have a couple more (Point One mono and a tatty mono Varislope).
Pretty sure it is humming less too. Really not an issue at the listening seat, though the JR149s are far from efficient. I’d certainly hear it through the Tannoys! The rumble filter very obviously works now too. It was hard to hear previously. Obviously something to leave switched out, but nice to know it works.
Did the rumble-filter too. Fiddly, but a good learning experience.
The slight burn-mark on the orange wire near the rumble filter was neither the cat nor me! It was there previously, almost certainly done by whoever tried to put the far too big mustard caps in nearby. I’m actually tempted to replace the two largest as they really don’t fit!
One of the black Hunts caps on the treble pot just shattered into a load of plastic shards as soon as I went near it, so I suspect it had been broken for years and may well have been the problem. The others measured around 0.04-0.07uF on the Fluke. The Peak ESR meter wanted nothing to do with any of them. I have a feeling it can’t measure really low values, but they were clearly screwed so no need to overthink it. The fact one was likely not even in one piece was almost certainly the issue. It is certainly sounding better and more balanced now. I’d not say 100% compared to the precision I’m used to with the Audio Synthesis attenuator, but not obviously off anymore and it sounds very nice indeed.
I seem to have lost the light on the front. May just be loose, or I may have trashed the bulb filament fiddling around moving it. No big deal. I’m kind of tempted to leave it as I was a little worried about heat damaging the ancient printing, though it does look cool. That said I will be using the AS Passion long-term, I just wanted to get this working. I’ll test the bulb later. I potentially have a couple more (Point One mono and a tatty mono Varislope).
Pretty sure it is humming less too. Really not an issue at the listening seat, though the JR149s are far from efficient. I’d certainly hear it through the Tannoys! The rumble filter very obviously works now too. It was hard to hear previously. Obviously something to leave switched out, but nice to know it works.
Barrymagrec
pfm Member
Goof job, my compliments to the cat.
Tony L
Administrator
Yes, I was kind of drawing a line under doing a full resistor rebuild as some are in absurdly awkward places, e.g. I think much if not all of the phono stage is soldered inside the layers of the input selector switch. Probably soldered in as the switch was assembled. I’m sure it would be possible to do it, but it would be incredibly awkward work. If I was going to do that sort of thing I’d far prefer to do two mono preamps and stack them as everything is so much simpler and there is much more space to work without the stacked nature of the stereo one. Makes sense as the stereo one is basically two monos in a box no bigger than one.
chiily
PFM Special Builder
Maybe a was unlucky, but i bought a pack of five similar bulbs from eBay only to find that they all gave up the ghost in quick succession, after only using each one for a few scant hours.
I ended up replacing the bulb with an LED. If you look half way down this page, there's an example of an LED running off the heater supply.
This site contains affiliate links for which pink fish media may be compensated.
Barrymagrec
pfm Member
Modern bulbs are bit like modern valves, some good, some not.
Tony L
Administrator
I’ve pinched the bulb from the mono Point One and its working again, so I’ll view the eBay order as spares. To be honest I’m really not bothered as whilst the light looks really cool (the logo lights up in a really good way) I‘d be concerned about heat damaging the ancient panel printing. I’d actually run without a bulb if it was going into regular use. The bulbs I ordered claim to be vintage NOS so they should be half decent.
PS I’m sufficiently triggered by the poor installation of the huge 0.22uF mustard caps I ordered some smaller (160V) ones so I can neaten up that area of the board. They really don’t need to be 400V! As I read the schematic nothing sees more than 135V aside from the 47K dropping resistor (which I also plan to replace as I have a nice fresh carbon film to hand). I’ve built up a reasonably useful stash of resistors and caps now, I’ve never got everything I need, but I’ve usually got some of it now!
PS I’m sufficiently triggered by the poor installation of the huge 0.22uF mustard caps I ordered some smaller (160V) ones so I can neaten up that area of the board. They really don’t need to be 400V! As I read the schematic nothing sees more than 135V aside from the 47K dropping resistor (which I also plan to replace as I have a nice fresh carbon film to hand). I’ve built up a reasonably useful stash of resistors and caps now, I’ve never got everything I need, but I’ve usually got some of it now!