I thought so...
Ok, any info on what to look for? I suposse an original SANYO IC would be difficult to obtain? Auction site and similar chinese sites offer anything decent or should be avoided as fakes?
ebay.com.au/STK3042-Original-SANYO-15P-SIP-IC-2-pcs-
USD $30.00 for two....advisable.
Seller looks perfectly genuine.
STK3042 is in three versions 3042, 3042 II and 3042 III.
I don't know if they are forward/backward compatible.....check before ordering.
Dan.
USD $30.00 for two....advisable.
Seller looks perfectly genuine.
STK3042 is in three versions 3042, 3042 II and 3042 III.
I don't know if they are forward/backward compatible.....check before ordering.
Dan.
Hmmm,
mine looks like that. STK3042 Voltage Amplifier for 40 to 90W AF Power Amp by Sanyo Lot of 2 | eBay
I'll try to find more info about the I and II versions.
Thanks for the quick answer and all the info.
mine looks like that. STK3042 Voltage Amplifier for 40 to 90W AF Power Amp by Sanyo Lot of 2 | eBay
I'll try to find more info about the I and II versions.
Thanks for the quick answer and all the info.
The link you give is for the very originals....I would avoid.
The packaging changed in later production.....better perhaps.
Dan.
The packaging changed in later production.....better perhaps.
Dan.
Hi Dan,
Agree on all counts now. I just hate it when folks jump to replacing the chip without any proof to support that the chip is faulty.
Hi dlamprou,
Some of the later marks had much lower THD, achieved through higher standby current. As long as the same number of pins are on the package, a later mark should work fine.
-Chris
Agree on all counts now. I just hate it when folks jump to replacing the chip without any proof to support that the chip is faulty.
Hi dlamprou,
Some of the later marks had much lower THD, achieved through higher standby current. As long as the same number of pins are on the package, a later mark should work fine.
-Chris
Any amplifier, even an op-amp for that matter, should have near zero voltage across the two input pins if it is working fine.
https://www.youtube.com/watch?v=7FYHt5XviKc
Gajanan Phadte
Hi Gajanan,
That is true, but for these STK voltage amplifiers you might see higher differentials. Don't get excited if op amps are not measurable while the STKs may be 10s of mV.
One word of caution here. Many amplifiers are sensitive to capacitance on the input pins. You can cause oscillation, DC offset or some various problems. Do not have any load on the speaker terminals! Also, be aware if you smell extra heat or hot parts (like the output zobel). Be aware of any other odd behavior.
Normally I train technicians to avoid doing this. Those things I mentioned can occur with everything in place and going to plan. Imagine what can happen if you short between pins or parts! What counts is the output pin as it is normally biased into the linear region. Look for big DC offsets (volts) or stuck to a power rail. Try not to mess around with signal input pins.
-Chris
That is true, but for these STK voltage amplifiers you might see higher differentials. Don't get excited if op amps are not measurable while the STKs may be 10s of mV.
One word of caution here. Many amplifiers are sensitive to capacitance on the input pins. You can cause oscillation, DC offset or some various problems. Do not have any load on the speaker terminals! Also, be aware if you smell extra heat or hot parts (like the output zobel). Be aware of any other odd behavior.
Normally I train technicians to avoid doing this. Those things I mentioned can occur with everything in place and going to plan. Imagine what can happen if you short between pins or parts! What counts is the output pin as it is normally biased into the linear region. Look for big DC offsets (volts) or stuck to a power rail. Try not to mess around with signal input pins.
-Chris
Is there a way to check STK3042 out of circuit?
By the way, it's very hard to find resistors with "fuse, fusible or flame retardant/proof" prefix.
Is it safe to use same specs, normal resistors?
I had to replace FR1, a CF 68 0,25W 2% with a flame-proof description in the Service manual. I just couldn't find any flame proof equivalent. Not in CF at least, only in MF type.
Any info/suggestions?
Thanks.
By the way, it's very hard to find resistors with "fuse, fusible or flame retardant/proof" prefix.
Is it safe to use same specs, normal resistors?
I had to replace FR1, a CF 68 0,25W 2% with a flame-proof description in the Service manual. I just couldn't find any flame proof equivalent. Not in CF at least, only in MF type.
Any info/suggestions?
Thanks.
Thanks...
In these modules, an open series resistor(external, around a 100 ohms) that biases the front end will make the output stick to one of the rails, which is the result of differential voltage on the input pins.
Gajanan Phadte
Hi dlamprou,
For future reference, never swap parts from a working channel into a blown channel.
-Chris
Use metal oxide resistors. That will satisfy the burn requirements. This is what I have always used for commercial servicing. All the manufacturers are satisfied with that.
No. They generate open flame when they burn out with enough surge energy. You can also use metal film resistors, but US ones, not the cheap Chinese ones.
You can go higher with the power level, but one step only. The tolerance of 2% (really?) is easily satisfied with 1% metal film resistors. They are not expensive. Shop Digikey, Mouser, Newark, Allied or Avnet.
Yes. Get an "equivalent circuit" for the STK pack and test it that way. The real Sanyo data sheets show this circuit. The only other way to truly test it is to stick it in circuit and power up.
For future reference, never swap parts from a working channel into a blown channel.
-Chris
akai amp
throw a cheap speaker on one output and jumper the relay contacts see what you get for output. possible reversed cap when re capping could cause dc to not allow the relay to trip?
throw a cheap speaker on one output and jumper the relay contacts see what you get for output. possible reversed cap when re capping could cause dc to not allow the relay to trip?
Well, the relay issue was fixed with the new fuse resistor. The amp is powering up again. Now only the crackling persists!
Chris, thank you for all your help!
I'll buy metal oxide resistors for FR1 (and FR2 as a pair), possibly for FR3 and FR4 for backup.
2% that's what I understand from the service manual (ERD2FC 1/4W 68R0G, Panasonic maybe?)
I'll study SANYO's data sheet about STK3042 and if it's manageable, then I'll try it. If not, its only 13euro for a new one, I'll choose the easy solution.
Thank you all, I'll report back with the STK verdict.
Hi dlamprou,
No problem!
For what it's worth, maybe just pick up the voltage amp IC and stick it in. We seem to be at that point, and you already checked and found the noise in the power amp section.
-Chris
No problem!
For what it's worth, maybe just pick up the voltage amp IC and stick it in. We seem to be at that point, and you already checked and found the noise in the power amp section.
-Chris
NOOOOO, not in my experience.
Fireproof safety resistors are used at higher cost for good reasons.....legal liability reasons.
MO and MF can withstand over power condition much better than carbon film types, and run incandescent for extended period.
"Metal oxide resistors can withstand higher temperatures than carbon or metal film resistors.
Read more Metal oxide film resistor » Resistor Guide"
Fusible, Non-Flammable Metal Film Leaded Resistors
Going higher in power rating is not advisable, especially when substituting a non-fusible resistor in this application.
The OP has established that the module is noisy, experienced techs have said that this is normal failure mode.
Just put a new pair of modules in and be done with it.
Be sure to perform initial power up with 40W/60W lamp in series with 240V power.
Usually good advice.
Dan.
Just put a new pair of modules in and be done with it.
You mean both STK3042 and STK2145?
Be sure to perform initial power up with 40W/60W lamp in series with 240V power.
Ok, that' easy to do.
Do you think that it's advisable to recap everything? The electrolytic's are all new.
Should I change other types too?
Thanks
You mean both STK3042 and STK2145?
Be sure to perform initial power up with 40W/60W lamp in series with 240V power.
Ok, that' easy to do.
Do you think that it's advisable to recap everything? The electrolytic's are all new.
Should I change other types too?
Thanks