all the diodes deemed to be dead should be removed and tested. use a 12 to 15 volt DC supply and 1k resistor to ground or ( - ). insert diode from + to open leg of resistor and measure the voltage across the resistor. the voltage = current in ma. if the diode is shorted or low resistance this will save the ma fuse in your meter.
Current diodes are just J-Fets with the source-gate connected together. They should measure like a diode one way and almost open the other (depending on your meter).
You can use LND150 or DN2540 D-Mosfets to create a current source. Their literature covers this and I've often used them. Benefit? They are good for 400 to 500 VDC breakdown depending on the device number you go with. Most are rated for 50 VDC or 100 VDC - again, depending on the type number.
-Chris
You can use LND150 or DN2540 D-Mosfets to create a current source. Their literature covers this and I've often used them. Benefit? They are good for 400 to 500 VDC breakdown depending on the device number you go with. Most are rated for 50 VDC or 100 VDC - again, depending on the type number.
-Chris
Anatech, good suggestion however he needs to know how much current is flowing to correctly bias the circuit. My guess is 5 ish ma.
if one channel is still good, he could measure that.
the bias level of the tube is a good indication. -3.4 volts (lithium battery) on a 5687 tube as the foil side shows the cathode grounded.
at 100v (on) plate and -3.4v on grid the tube curves show about 10 -12 ma of current
we would need to know the plate voltage rather then the B+ value to attain current flow.
this tube is very similar to 6922.
if one channel is still good, he could measure that.
the bias level of the tube is a good indication. -3.4 volts (lithium battery) on a 5687 tube as the foil side shows the cathode grounded.
at 100v (on) plate and -3.4v on grid the tube curves show about 10 -12 ma of current
we would need to know the plate voltage rather then the B+ value to attain current flow.
this tube is very similar to 6922.
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Thanks guys I have enough info to probably have a stab at fixing the amp and making it work again but as a Zanden owner I want to restore the product to its original standard using the correct parts. In any other business other than Hi-Fi this would not be an unreasonable request. So to test the water I enquired about buying the latest Zanden 9600 amps from the UK dealer as a retirement gift to myself.
He phoned me back from the Adriatic and we discussed the differences in sound between the 9500, when I asked what support I could expect for £56,000 pound amplifier he stated the product was covered by UK law for two years, and stated his number 2 would cover if and when he retires. I asked what would happen if 5 years into my retirement I experienced a problem. At this point he related the call to my emails and changed his tone significantly. He stated he replies to all emails in 12 hours although I've yet to locate the response.
He said such a situation would be subject to out of guarantee repair but they would provide no technical support what so ever. I stated I have not even been offered any out of guarantee service at all at which time he terminated the call.
As a business man myself I find this attitude unbelievable, so basically after two years you are on your own – how about that for product depreciation. I hope this attitude is not representative of the brand – lets see.
He phoned me back from the Adriatic and we discussed the differences in sound between the 9500, when I asked what support I could expect for £56,000 pound amplifier he stated the product was covered by UK law for two years, and stated his number 2 would cover if and when he retires. I asked what would happen if 5 years into my retirement I experienced a problem. At this point he related the call to my emails and changed his tone significantly. He stated he replies to all emails in 12 hours although I've yet to locate the response.
He said such a situation would be subject to out of guarantee repair but they would provide no technical support what so ever. I stated I have not even been offered any out of guarantee service at all at which time he terminated the call.
As a business man myself I find this attitude unbelievable, so basically after two years you are on your own – how about that for product depreciation. I hope this attitude is not representative of the brand – lets see.
Whew, future purchasers of these pieces will undoubtedly run into this thread and may change their minds about purchasing.
IMO, there's not likely to be anything in there that needs replacing that you can't get from Mouser. It's ridiculous that they won't at least provide the circuit diagram.
IMO, there's not likely to be anything in there that needs replacing that you can't get from Mouser. It's ridiculous that they won't at least provide the circuit diagram.
Hi petertub,
I'm afraid that most manufacturers regard their circuit as a big secret. You are not likely to have access to service information from almost all manufacturers and distributors. I generally have a few repair units at a time that are in this situation.
I believe that any product sold in my country should surrender all technical documentation suitable for service uses into a library. If that company goes out of business, these documents can be released. Also, any service person should have free access to service info when a particular unit is out of warranty.
I've spent a lifetime battling silly companies, the end user is always the big loser in this situation - and often the better repair people lose time on them as well.
-Chris
I'm afraid that most manufacturers regard their circuit as a big secret. You are not likely to have access to service information from almost all manufacturers and distributors. I generally have a few repair units at a time that are in this situation.
I believe that any product sold in my country should surrender all technical documentation suitable for service uses into a library. If that company goes out of business, these documents can be released. Also, any service person should have free access to service info when a particular unit is out of warranty.
I've spent a lifetime battling silly companies, the end user is always the big loser in this situation - and often the better repair people lose time on them as well.
-Chris
I guess the current diodes are from these series
http://uk.farnell.com/american-power-devices/1n5314/diode-current-regulator/dp/1651074
http://uk.farnell.com/american-power-devices/1n5314/diode-current-regulator/dp/1651074
We "consumers" don't have to buy from these "silly companies", there is enough good audio equipment to fill our needs.
In addition, those "secret devices" are secret for a reason ; they are plain snakeoil and exposing their circuits will show that.
Good sound reproduction is best done by simple solutions !
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