Sorry to resurrect an old thread, but I just ordered all new transistors and zeners for my long dead 4240. I'm hoping that'll fix it like it fixed the others in this thread. Same symptoms, the mains fuse will blow as if there is a short. It won't cost much and if it works I'll have brought back to life a nice amp. It cost about $30, if that, and I bought extras of everything.
Another blown 4240
I just bought a Creek 4240 (v1.2 circuit board) on ebay, and it's power supply fuses are blown. I just ordered new ones, but strongly suspect I'll have to replace the output transistors, having gone through this exercise a few times in the past with Creek 4040 amps.
@zacster, any luck? What transistors did you order and from where? I'm waiting to hear back from Creek themselves, in case they sell a replacement kit.
BTW I found a high-res v1.2 schematic which I'm attaching...
I just bought a Creek 4240 (v1.2 circuit board) on ebay, and it's power supply fuses are blown. I just ordered new ones, but strongly suspect I'll have to replace the output transistors, having gone through this exercise a few times in the past with Creek 4040 amps.
@zacster, any luck? What transistors did you order and from where? I'm waiting to hear back from Creek themselves, in case they sell a replacement kit.
BTW I found a high-res v1.2 schematic which I'm attaching...
Creek don't provide servicing parts or kits but the semis and components are mostly common types, still available cheap from major distributors like Digikey and Mouser. The logic-level BUK553 output mosfets are obsolete though, so the advice from the designer earlier in this thread, for this and several similar models, is to fit IRF540L which is also a logic level type, not the IRF540N which was also mentioned but is a standard type mosfet that requires a much higher offset to its gate drive voltage.
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I'm surprised! I replaced the blown PS fuses that came with the amp (incorrectly slow-blow 5 amp) with the correct T3.15 fuses and the amp works perfectly -- even on my workbench and with low-end KEF K120 speakers I hear a nice amount of depth behind the speakers.
For future reference, are IRF540L transistors the same as IRL540? I can't seem the find the former in stock anywhere.
For future reference, are IRF540L transistors the same as IRL540? I can't seem the find the former in stock anywhere.
I was looking for this thread that I remember when I tried to fix my 4240 so I could get the transformer specs. I'm looking to build one of the PassLabs DIY amps that are popular here and thought maybe I could save some pennies by reusing the transformer.
I never did get my 4240 to work of course since I'm looking to cannibalize it for parts now.
I never did get my 4240 to work of course since I'm looking to cannibalize it for parts now.
The amp using all the zener diodes are same 15v, you can check the schematic in #22 and you can buy zener diode P/N 1N4744A 15v 1w to replace.
keep blowing fuses maybe a short in the output transistors, please check this.
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Fixed: intermittent static
My 4240 had an intermittent static noise in one channel for a few years, which seemed to come back when I had not turned it on for a time. Last friday I suffered through the static all day and opened it up in the evening to try to find the cause.
I first took the lid off and touched each component with a pencil while powered on, to see if I could make the static come/go. It seemed that flexing the PCB stopped the static, so I disassembled the unit to look for a cracked trace. Long story short: there was a bad solder joint on the leg of one of the low-power transistors. After touching up the solder on the underside of the PCB the amp is dead quiet again.
(This gives me a new appreciation for what a great amp this is. Easy to disassemble and troubleshoot. The PCB traces are generous and very unlikely to break. The circuit is relatively simple and well laid out. I'm impressed with the use of clamps to hold the power transistors to the heat sink. And of course that huge toroidal transformer... All this in an enclosure half the size of other similar-wattage amps.)
My 4240 had an intermittent static noise in one channel for a few years, which seemed to come back when I had not turned it on for a time. Last friday I suffered through the static all day and opened it up in the evening to try to find the cause.
I first took the lid off and touched each component with a pencil while powered on, to see if I could make the static come/go. It seemed that flexing the PCB stopped the static, so I disassembled the unit to look for a cracked trace. Long story short: there was a bad solder joint on the leg of one of the low-power transistors. After touching up the solder on the underside of the PCB the amp is dead quiet again.
(This gives me a new appreciation for what a great amp this is. Easy to disassemble and troubleshoot. The PCB traces are generous and very unlikely to break. The circuit is relatively simple and well laid out. I'm impressed with the use of clamps to hold the power transistors to the heat sink. And of course that huge toroidal transformer... All this in an enclosure half the size of other similar-wattage amps.)
huge toroidal transformer means it can delivery more current to the output therefore the amp can be easily to handle the speaker in different load situation.
Creek 4240
Thanks Pat. I have the schematics and some components don't match the actual PCB. For example, the ZVP3310 is substituted for a UP 2020?? So, this is the second time the internal fuses blow. Again, one output transistor blew BUK553. Its hard to find what component is at fault, so I am pulling nearly every transistor. I'm just a basic hobbyist but am determined to find the component. Any suggestions??
Anthony
Thanks Pat. I have the schematics and some components don't match the actual PCB. For example, the ZVP3310 is substituted for a UP 2020?? So, this is the second time the internal fuses blow. Again, one output transistor blew BUK553. Its hard to find what component is at fault, so I am pulling nearly every transistor. I'm just a basic hobbyist but am determined to find the component. Any suggestions??
Anthony
are you using a Dim Bulb Tester (google it),as this will greatly assist you powering and being able to test components without blowing things up.
Have you disconnected the Supply and tested it separately? Sounds like either a PSU problem, or high-power transistor shorted. Granted both of those problems, could easily have damaged other things before the fuse blew. Thoughts only, as I didn't read thru whole thread.
Have you disconnected the Supply and tested it separately? Sounds like either a PSU problem, or high-power transistor shorted. Granted both of those problems, could easily have damaged other things before the fuse blew. Thoughts only, as I didn't read thru whole thread.
Yes, building a tube amp(not much tubes) and servicing it by tubes replacement are more easy than a solid state amp.
To repair a solid state amp, if you measure each transistor pins voltages and you will know these transistors working condition ok or not, in this way you will find out the problem items to fix.
If you have time and willing to repair your amp, please inform us your amps conditions and some voltages measurement if possible, we can estimate the amp problem.
In the ver. 1.2 schematic, it is using a mosfet UP2020, so that ZVP3310 and UP2020 should be compatible.
I checked ver. 1.2 and other model 4330 schematic, they are almost same circuit design, I think your amp model mosfet over current caused the problem.
Both schematics said that "Q8 must touch heatsink", when Q8 touched the heatsink, it's Vbe will reduce and decrease the mosfet idle current when heatsink temp raise.
In the model 4330 the idle current reduced to 70mA (7mv resistor voltage), model 4240 idle current is high at 110mA (11mv resistor voltage). I think the designer realize too high idle current will make the amp over current trouble.
Please double check and make sure "Q8 and Q108 must securely touch the heatsink" and reduce the "idling current with a 7mv resistor voltage (70mA)".
Attachments
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You test each transistors, if ok put back to the amp, replace any bad transistors and mosfet, check Q8/Q108 touching heatsink and set the new idle current.
If you never replace your power supply caps and other caps, please consider to replace them with new ones.
A bit of warning...on the diagram on the left, Q18 is marked as VP2020, not UP2020, but the point is that both marks are wrong...there are no VP2020 and UP2020 around, there is only VP2020L but using it is not adequate because it is a low threshold Vgs(th) p-ch M-fet. For Q18, the "normal" threshold Vgs (th) M-fet should be used, in contrast, for output stage low-Vgs (th) M-fets (so-called logic-level M-fets) MUST be used like Fairchild HUF76639P3, Fairchild/IR IRL640 or original Philips BUK555-100A(B), BUK555-200A(B).
So...the diagram on the left probably should have written Supertex VP2210, or the already mentioned Zetex ZVP3310 or Supertex VP2450 or even IRFF9110 (TO39 housing) and IRF9610 (TO220 housing) could be used, but one have to be very careful about pinout.
So...the diagram on the left probably should have written Supertex VP2210, or the already mentioned Zetex ZVP3310 or Supertex VP2450 or even IRFF9110 (TO39 housing) and IRF9610 (TO220 housing) could be used, but one have to be very careful about pinout.
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