Schematics for Elite Townshend 600c Preamplifier?
- Thread starter Sibbers
- Start date
Paul R
pfm Member
Assuming Townshend cannot help, presumably the 600C is from many business incarnations ago, it's a simple preamp, it should be amenable to looking hard, thinking hard and probing with a meter and oscilloscope.
If you posted a description of the effect of the fault and some internal photos perhaps progress could be made. (I'd like to see inside one regardless....)
If you posted a description of the effect of the fault and some internal photos perhaps progress could be made. (I'd like to see inside one regardless....)
Sibbers
Earthling
The fault, IIRC, was a buzz I think. Possibly voltage leaking? I am not really even qualified guess.
Let’s see if we can get some pics sorted.
Townshend not willing to share as I understand.
Pretty sure the old man got his original one from Max many years back very early on in their production, but this one is second hand bought more recently, then serviced and after around a year of use a buzz or noise developed.
I wonder if it’s worth asking GT Audio.
Thanks for the comments - let’s see if we can organise getting some pics posted and a better description.
Let’s see if we can get some pics sorted.
Townshend not willing to share as I understand.
Pretty sure the old man got his original one from Max many years back very early on in their production, but this one is second hand bought more recently, then serviced and after around a year of use a buzz or noise developed.
I wonder if it’s worth asking GT Audio.
Thanks for the comments - let’s see if we can organise getting some pics posted and a better description.
martin clark
pinko bodger
Oh, a slowly-developed, common-or-garden buzz/humm is likely /easily/ sorted.
Very much not likely a transistor; just an aged capacitor or two!
Very much not likely a transistor; just an aged capacitor or two!
rontoolsie
pfm Member
The Townsend electronics were designed by Geoff Mead, who happens to be an old friend of a guy I know pretty well (he is using the DBL PAXO that I had consigned many years ago).
If you are interested, I could maybe scrounge up the contact info of Geoff or possible scare up a schematic for the 600c.
If you are interested, I could maybe scrounge up the contact info of Geoff or possible scare up a schematic for the 600c.
Sibbers
Earthling
Mate, that would be ace of you could give it a go. What a cracking bit of luck if this turns up the goods - thanks.
rontoolsie
pfm Member
This forum is an invaluable resource of information on legacy/vintage gear. The name of the designer and his friendship wilh him were only revealed to me in the last email he sent me a couple weeks ago, so this is indeed a stroke of luck.
I have already e-mailed JK about your dilemma and expect a response in the next day or so.
I will let you know.
Sibbers
Earthling
You’re a gent, thank you regardless of the outcome.
My old man sent me an email this morning with the following about the fault and his attempts to eliminate stuff.
Good morning.
Thanks for all that. There are 27 caps in the 600c - 2 in the power supply and 25 in the preamp. it was totally recapped a year ago by an audio expert. The noise isn't a buzz (sadly as that's usually an easy fix). the preamp is quiet through the line imputs so the problem of lf clicking is in the phono stage - probably on the mc side. The cartridge is quieter with a step up through the mm imput but there is occasional bottoming in the left speaker on very low lf. The speaker itself does not have this on other amplification - not a speaker problem. The oscope reveals no problems and all the solder joints have been remade. The noise resembles lf clicking, hence a transistor is suspected of being the problem. A schematic would be really handy.
The team that you'e got on this is kind of exciting - please can you continue with hunt
Teamwork to make the dream work 
Thanks so much gents.
My old man sent me an email this morning with the following about the fault and his attempts to eliminate stuff.
Good morning.
Thanks for all that. There are 27 caps in the 600c - 2 in the power supply and 25 in the preamp. it was totally recapped a year ago by an audio expert. The noise isn't a buzz (sadly as that's usually an easy fix). the preamp is quiet through the line imputs so the problem of lf clicking is in the phono stage - probably on the mc side. The cartridge is quieter with a step up through the mm imput but there is occasional bottoming in the left speaker on very low lf. The speaker itself does not have this on other amplification - not a speaker problem. The oscope reveals no problems and all the solder joints have been remade. The noise resembles lf clicking, hence a transistor is suspected of being the problem. A schematic would be really handy.
The team that you'e got on this is kind of exciting - please can you continue with hunt
Thanks so much gents.
rontoolsie
pfm Member
Follow up from Geoff Mead's friend...
Geoff worked for Max in the later years. He designed the Transformer coupled preamp and a few others. However I will see if I can get hold of him and ask the question.
Geoff worked for Max in the later years. He designed the Transformer coupled preamp and a few others. However I will see if I can get hold of him and ask the question.
Arkless Electronics
Trade: Amp design and repairs.
I'm wondering if it IS the speaker... LF woofer wobble from vinyl causing the speaker to make fairly large excursions which make a click from some sort of mechanical problem with woofer
Sibbers
Earthling
I remember going through some steps to eliminate the amp. He has two, one a Cyrus with no fault and the other an MF SA80 that you helped out with (cheers mate!). Anyway the SA80 is the amp that hears and passes on the fault, so wanted to eliminate that - I don’t remember eliminating the speaker but I’m sure he would have done, as we got down to the fault existing in the arm/cartridge or preamp, and then eventually the pre.
Good shout tho. I can recall spending hours pulling a PC apart because the display just wouldn’t work before discovering the fault was with the monitor which just needed unplugging from the mains for a few minutes.
It’s a quick a simple test so I’ll pass it on and see if it powers up his inner angry troll. He’s not long had new woofers, but they’re 1SC’s and he plays them at concert levels. If they are faulty I think he will be secretly delighted at the idea of spending money on fancy new (second hand, British made) speakers.
Good shout tho. I can recall spending hours pulling a PC apart because the display just wouldn’t work before discovering the fault was with the monitor which just needed unplugging from the mains for a few minutes.
It’s a quick a simple test so I’ll pass it on and see if it powers up his inner angry troll. He’s not long had new woofers, but they’re 1SC’s and he plays them at concert levels. If they are faulty I think he will be secretly delighted at the idea of spending money on fancy new (second hand, British made) speakers.
Arkless Electronics
Trade: Amp design and repairs.
Up thread says "scope reveals no problems"... plus it just doesn't sound like any amplifier fault scenario (not to say it isn't some fault seen once in 30 years even by the likes of myself or a bizarre peculiarity of that pre amp).
Recent new woofers and concert levels supports the speaker hypothesis!
Recent new woofers and concert levels supports the speaker hypothesis!
PigletsDad
My intelligence test came back negative.
Could it just be that it has extended LF bandwidth, and warps are coming through and making the woofers bottom? If the power amp has some LF roll-off this won't be a problem, but a model with excess subsonic bandwidth would.
I predict the clicking will be every 60/33 = 1.82 seconds, or a multiple of that. Count the clicks in say 20s. If you get 11, or a multiple of 11, it is almost certainly related to warp LF.
I predict the clicking will be every 60/33 = 1.82 seconds, or a multiple of that. Count the clicks in say 20s. If you get 11, or a multiple of 11, it is almost certainly related to warp LF.
Sibbers
Earthling
It is possible, like Jez says above, there's always a rare occasion but its probably not that as the fault doesn't occur with other preamps and amps that have been included in trying to eliminate it. The old fella is very confident about where the source of the problem is, but the ease with which it takes to switch the inputs around should do the job - its one (left) channel only and only on the phono stage. Always appreciate a good suggestion tho, so cheers! I did think the same btw and I didn't know about the click counting thing! That's pretty cool, do you know why that is? Be gentle.
Arkless Electronics
Trade: Amp design and repairs.
I wouldn't expect it to be that predictable and for there to be any point in "click counting" personally. Even visibly perfectly flat records give loads of "woofer wobble" IME. Arm cartridge resonance at around 10Hz is more like the frequency involved plus lower frequencies from actual warp riding. A pattern is visible but different for each record.
Your dad should try swapping the channels over to see if it remains in the left speaker.
Your dad should try swapping the channels over to see if it remains in the left speaker.
PigletsDad
My intelligence test came back negative.
It is possible, like Jez says above, there's always a rare occasion but its probably not that as the fault doesn't occur with other preamps and amps that have been included in trying to eliminate it. The old fella is very confident about where the source of the problem is, but the ease with which it takes to switch the inputs around should do the job - its one (left) channel only and only on the phono stage. Always appreciate a good suggestion tho, so cheers! I did think the same btw and I didn't know about the click counting thing! That's pretty cool, do you know why that is? Be gentle.
As Jez says, most often the arm resonance stuff dominates, somewhere round 10Hz. But warps can be very big, and if they are to blame, they will come round in a pattern once per revolution. LP records are 33rpm, so one revolution is 60/33 seconds. In 20s, you get 11 revolutions. So if (however unlikely) the clicks are to do with rotation of the record, then they should be happening as 11 per 20s, or a multiple if you get more than one event causing a click per revolution.