Hi everyone.
I'm new here, but this seems like a great place to ask for advice.
I have a little Leak Delta 70 which I've been using for a while with a pair of Dovedale IIs.
I like it; It serves its purpose well.
The only thing is, recently I noticed that the two channels are not even in frequency response. One side has a fair bit more bass than the other.
It's not so bad that you'd notice all the time, but If you look for it, it's definitely there.
I swapped my input rcas, and the speaker outputs to prove where the problem was.
It proved to be with the amp.
Inside the amp, there are four cards which I removed, cleaned and reseated.
I also swapped them around from left to right to rule them out of the equation.
The problem doesn't lie with them.
Really what I'm asking is, what would you advise? Full recap? Is there anything specific to look at?
I wouldn't say I'm especially knowledgeable with electronics, but I get the basics and am certainly capable of replacing components, etc.
Maybe you'd bin it and buy a better amp?
Any advice is welcome.
Thank you.
I'm new here, but this seems like a great place to ask for advice.
I have a little Leak Delta 70 which I've been using for a while with a pair of Dovedale IIs.
I like it; It serves its purpose well.
The only thing is, recently I noticed that the two channels are not even in frequency response. One side has a fair bit more bass than the other.
It's not so bad that you'd notice all the time, but If you look for it, it's definitely there.
I swapped my input rcas, and the speaker outputs to prove where the problem was.
It proved to be with the amp.
Inside the amp, there are four cards which I removed, cleaned and reseated.
I also swapped them around from left to right to rule them out of the equation.
The problem doesn't lie with them.
Really what I'm asking is, what would you advise? Full recap? Is there anything specific to look at?
I wouldn't say I'm especially knowledgeable with electronics, but I get the basics and am certainly capable of replacing components, etc.
Maybe you'd bin it and buy a better amp?
Any advice is welcome.
Thank you.
If bass is lacking that is a fairly sure sign a cap has "lost goodness", either in value or high ESR.
It's always nice to find the fault properly however you really need a scope and signal generator for that. There is also the distinct possiblity that several caps are all below parr... which a scope would show of course.
You can bridge electrolytics as a rough and ready test (or rather tag another across the one already in circuit) and see if that alters things.
On something of this age a full recap is needed though.
You can bridge electrolytics as a rough and ready test (or rather tag another across the one already in circuit) and see if that alters things.
On something of this age a full recap is needed though.
As soon as I notice some symptom like odd frequency response, or out of balance, or low power (Vac out into known resistance) on an old audio product, I order all the electrolytic caps, or $50 worth anyway, and start near the power transformer replacing one at a time. E-caps are sealed with rubber and just like old tires, are bound to leak sometime after 15 years. Anything that makes it better, thumbs up. Worse, whatever I just did is the problem, back up and look again. If the response end up fine, I still replace all the electrolytics as long as the device is older than 20 years. The rubber water seal is attacked by air sitting still or powered up.
I replace film or disc caps for cause, not based on the calender. I had a channel imbalance in my 1961 build PAS2 that turned out (after tube swaps, power supply checkes, and new B+ e-cap) to be a peper cap whose wax case was burnt through in 1961 and hidden by the builder. I stopped replacing at the other channel match at that cap, as the polyester caps I was using made the preamp a bit too trebly. By contrast my upgraded organs (1968, 1964) have hundreds of film and disk caps that are not a problem.
Disc caps can also fail, but not often. I have to have a symptom in an area to make me suspect one before I install one. Disks are prevalent in TV's CRT's and switcher power supplies, so I usually have something close in value and 1000 V rated for debug before I order a CPO 10% disk cap replacement. I organize used caps and resistors in bags by decade value.
The leak 70 does have some potentiometers used as controls, and those wear out too based on # of cycles up and down. You can measure them with a meter to see what you have got if you disconnect one leg. Spraying with contact cleaner (warning very flammable, no open flame or electricity on or off) can provide some temporary relief but not usually on something that has been used a lot.
Search, somebody did a simulation that the distortion of the delta 70 went down as newer generations of output transistors were installed. 2n3772->2n3055->Tip3055. I think the faster Ft was doing the good.
I replace film or disc caps for cause, not based on the calender. I had a channel imbalance in my 1961 build PAS2 that turned out (after tube swaps, power supply checkes, and new B+ e-cap) to be a peper cap whose wax case was burnt through in 1961 and hidden by the builder. I stopped replacing at the other channel match at that cap, as the polyester caps I was using made the preamp a bit too trebly. By contrast my upgraded organs (1968, 1964) have hundreds of film and disk caps that are not a problem.
Disc caps can also fail, but not often. I have to have a symptom in an area to make me suspect one before I install one. Disks are prevalent in TV's CRT's and switcher power supplies, so I usually have something close in value and 1000 V rated for debug before I order a CPO 10% disk cap replacement. I organize used caps and resistors in bags by decade value.
The leak 70 does have some potentiometers used as controls, and those wear out too based on # of cycles up and down. You can measure them with a meter to see what you have got if you disconnect one leg. Spraying with contact cleaner (warning very flammable, no open flame or electricity on or off) can provide some temporary relief but not usually on something that has been used a lot.
Search, somebody did a simulation that the distortion of the delta 70 went down as newer generations of output transistors were installed. 2n3772->2n3055->Tip3055. I think the faster Ft was doing the good.
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Yes, I'd suspect an old dried up electrolytic cap first.
IIRC the Delta 70 is the same as Leak Stereo 70. These old amps have speaker output coupling caps. These are C34L and C34R which are largish 2200uF electrolytics mounted horizontally on the side panel between the volume pot and the power transformer.
Grab a 2200uF 63V or larger and temporarily connect it across the C34 for the channel lacking bass.
All the other signal carrying electrolytics are on the plug in boards, so if it is a dried up electro it must be one of the C34's
The larger power supply electros (C2,3,4,6,7) are common to both channels, so they can't cause a single channel fault like this.
IIRC the Delta 70 is the same as Leak Stereo 70. These old amps have speaker output coupling caps. These are C34L and C34R which are largish 2200uF electrolytics mounted horizontally on the side panel between the volume pot and the power transformer.
Grab a 2200uF 63V or larger and temporarily connect it across the C34 for the channel lacking bass.
All the other signal carrying electrolytics are on the plug in boards, so if it is a dried up electro it must be one of the C34's
The larger power supply electros (C2,3,4,6,7) are common to both channels, so they can't cause a single channel fault like this.
Thank you, Essb, and indiana.
That's some really useful information. 🙂
I'll look into that.
Cheers.
That's some really useful information. 🙂
I'll look into that.
Cheers.
Hi there,
Just wanted to follow up for anyone reading this in future.
I didn't have a suitable cap lying around, but I swapped the two 2200uF caps in question and the problem did switch channels.
Simple enough, but man, that would have taken me forever to find.
Thank you once again.
Just wanted to follow up for anyone reading this in future.
I didn't have a suitable cap lying around, but I swapped the two 2200uF caps in question and the problem did switch channels.
Simple enough, but man, that would have taken me forever to find.
Thank you once again.
Sorry to trouble you all, but I got my replacement caps today and fitted them.
I think I've had the single unluckiest day in the world ever, but I'll not go into that.
Long story short, I have a fault on one of the two removable cards in the centre of the amp.
I know it's isolated to the card; I can run either channel of the amp with the good card fitted and the other removed.
The two ceramic resistors, r52+r53) heat up on the bad board until the fuse blows, regardless of what slot the card is fitted to.
C33,c29 and c32 are not at fault.
Also, does anyone know the part number for T9?
Thanks you in advance, You've been so helpful.
I think I've had the single unluckiest day in the world ever, but I'll not go into that.
Long story short, I have a fault on one of the two removable cards in the centre of the amp.
I know it's isolated to the card; I can run either channel of the amp with the good card fitted and the other removed.
The two ceramic resistors, r52+r53) heat up on the bad board until the fuse blows, regardless of what slot the card is fitted to.
C33,c29 and c32 are not at fault.
Also, does anyone know the part number for T9?
Thanks you in advance, You've been so helpful.
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ok, that makes sense.
I tested and switched out T9 and we're back on a winner.
Parts ordered-waiting game begins. 🙂
Thanks once again.
I tested and switched out T9 and we're back on a winner.
Parts ordered-waiting game begins. 🙂
Thanks once again.
Story of my life. There's still time though. 😀
I've an ongoing issue with an akai 4 track; Maybe I'll see you chaps in another thread sometime. 🙂
Thanks again.
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