Hey,
I've got a broken Thule IA150B that I wanted to repair. I want some help on where to start, maybe it's a broken DC-bridge? ,
Anyway, the amplifier turns on just fine and the screen lights up, relay clicks and input selector works. However, the signal is not sent to the speakers. Instead I hear a rather loud humming noise around 200-300Hz which is not affected by volume control. All fuses seem to be ok, capacitors looks good on a first look. Only visual error is that the transformer is not attached . Any ideas?
Attached is two images and the service manual.
BR,
Moe
I've got a broken Thule IA150B that I wanted to repair. I want some help on where to start, maybe it's a broken DC-bridge? ,
Anyway, the amplifier turns on just fine and the screen lights up, relay clicks and input selector works. However, the signal is not sent to the speakers. Instead I hear a rather loud humming noise around 200-300Hz which is not affected by volume control. All fuses seem to be ok, capacitors looks good on a first look. Only visual error is that the transformer is not attached . Any ideas?
Attached is two images and the service manual.
BR,
Moe
Attachments
I would check with an oscilloscope where the odd frequency is coming from first and then look for bad ground connections and good supply lines.
OK so I noticed a DC-voltage on S3 (left) but not on S4(right). This voltage was also present on P1 (left) but not on P101 (right). I then removed S3 and S4 and the DC-offset disappeared, but insted C122 went up in smoke. So I'm guessing there's something wrong with the REG9 or REG10, but I have no clue. Any help before I burn more components?
BR,
Moe
BR,
Moe
Perfectly dead capacitors can look perfectly good. An oscilloscope will tell quickly. Or measure the DC and ac on the main filter caps. The ac should be a lot lower than the dc.
I don't have access to an oscilloscope at the moment. Any way to determine which is bad and which is not with a multimeter?
So I have picked it apart more tonight. Now I can clearly see that some components are burnt. First picture shows C122 and the capacitors around it, second one the right channel and the third shows REG1 and REG2. Any idea how I can measure if the REG1/REG2 are ok?
Attachments
I think they have been running on high temperature for long period,not necessary burnt.
Anyway,unless you are able to isolate the load(circuit) from the regulator themselves,or else hard to determine are they confirm OK or not.
Yes,u can still try to measure the output voltages of the regulators with load connected,since I don't think that you want to cut the PCB traces.
Ok! The plan is to change all the 100uF 35V capacitors and see what happens. I have measured all the diodes and they seem fine.
Any other ideas?
Any other ideas?
You can use a multimeter on the main caps. Of course, there should be DC. Switch to AC and measure the ripple. Do this with no signal and no load, and with a load, still no signal.
Since yours is humming with no signal, these numbers should be enough to determine. I recently repaired an amp that didn't hum, but even with a very low signal level, the ripple on the failing main caps would cause a raspy distortion each cycle when the required output voltage tried to go above what was left in the caps between the peaks of the rectified AC coming in.,
Since yours is humming with no signal, these numbers should be enough to determine. I recently repaired an amp that didn't hum, but even with a very low signal level, the ripple on the failing main caps would cause a raspy distortion each cycle when the required output voltage tried to go above what was left in the caps between the peaks of the rectified AC coming in.,
Changed the the C21-C24, C121-C124 and C29-C32. Still same issue, still +19V DC offset oblekt channel on fuses, still loud humming in speakers. What could be faulty? AC/DC-converter? Measured the diodes bit they seem fine. Out of ideas, grateful for any help!
DDave: You mean the four large 10mF caps?
DDave: You mean the four large 10mF caps?
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This amp is unconventional to say the least - what a headache. (Quite possibly the designer was doing power mixers or stuff like that otherwise.) The mains transformers secondaries could be used to generate some +/-40(ish) V supplies, but instead of that, they decided that they'd rather build a power amp with a fully balanced (BTL) output that is running on +/-20 V, with one secondary winding per channel. They are effectively generating 2x 40 V floating, which are then balanced around ground potential using a rail splitter (R60/61/68/69, C29/30 et.al.). This is not the most robust setup, balance is relatively easily upset if, say, things are going wrong in the power amp.
The +/-26 V regulated voltages you were looking at are feeding the first power amp stages. They already have to be generated using a voltage doubler setup. In case of bad voltage balance, it is easily possible to blow one of C21/22/121/122.
Next you should check supply voltages WRT ground - +/-26 V reg, +/-20 V (both channels). Both P1 and P101 should carry +20V, so if one doesn't something is clearly wrong there, and if it's just a shorted cap or open resistors in the rail splitter. I suspect you'll eventually find a power amp problem.
The +/-26 V regulated voltages you were looking at are feeding the first power amp stages. They already have to be generated using a voltage doubler setup. In case of bad voltage balance, it is easily possible to blow one of C21/22/121/122.
Next you should check supply voltages WRT ground - +/-26 V reg, +/-20 V (both channels). Both P1 and P101 should carry +20V, so if one doesn't something is clearly wrong there, and if it's just a shorted cap or open resistors in the rail splitter. I suspect you'll eventually find a power amp problem.
Hi sgrossklass, thanks for taking your time! I have changed all the 100uF capacitors.
I have some unbalance on the left channel, I get +45V and -15V at +/-20. On the right one I get +/-30V at +/-20V pins, so I am a little bit high but even between +/-.
I have checked the resistors and they seem fine, but I will resolder them just to be sure. Any other ideas here?
I have some unbalance on the left channel, I get +45V and -15V at +/-20. On the right one I get +/-30V at +/-20V pins, so I am a little bit high but even between +/-.
I have checked the resistors and they seem fine, but I will resolder them just to be sure. Any other ideas here?
The most important thing is the remove of both voltage enhancers include regulators and all parts between S5/S8 and Reg7/Reg10, because there is no space for absolute necessary heatsinks for the regulators. At my repair devices of IA150B many years ago I put in a passive filter chain consist of two 100R resistors and two 100uF electrolytics (for each rail in both channels).
The now present disadvantage is the fact, that the voltage value for the front end of the power amp section is much lower than before (i. e. lower undistorted output voltage and thus lower output power). Under normal home audio conditions this disadvantage isn't audible (approximately -6db loss for max. SPL). The main advantage is now no burning effects arround this area.
But there are a lot of other steps necessary to get sufficient reliability over the years, e.g. the use of 4 pcs 4700uF/100VDC (instead 10000uF/63V) capacitors and heatsinks for the 5Vdig and +/-7V5 regulators. Best solution is the use of external plug-in power supplies for those low voltages, because the creating of such low voltage from the voltage of power amp without heating is not posible.
Check also out post #30 under
http://www.diyaudio.com/forums/solid-state/126352-what-happen-thule-audio.html
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It's hard repairing a device without a scope, and some skill is also required.
Moeses, if you happen to live in the vicinity of Gothenburg perhaps I can be of assistance.
According to the schematics, the amp is without negative feedback. I imagine the amp becomes quite hot - a high bias will probably be needed to keep the cross over dist at a resonably low level.
It has probably a vivid and dynamic sound but the lack of NFB may give it some harshness at low levels.
Actually, that balanced design reminds a bit of Nelson Pass' "super symmetry" amps which he has a patent for. Nelson claims that the principle reduces distortion, but I don't think so, but it has probably some other advantages.
One may be that common mode signals won't be present att the speaker terminals at all. On a "normal" balanced "dual amp", a common mode signal will indeed be present at the terminals, but in phase with each other so that no current will flow through the speakers.
Moeses, if you happen to live in the vicinity of Gothenburg perhaps I can be of assistance.
According to the schematics, the amp is without negative feedback. I imagine the amp becomes quite hot - a high bias will probably be needed to keep the cross over dist at a resonably low level.
It has probably a vivid and dynamic sound but the lack of NFB may give it some harshness at low levels.
Actually, that balanced design reminds a bit of Nelson Pass' "super symmetry" amps which he has a patent for. Nelson claims that the principle reduces distortion, but I don't think so, but it has probably some other advantages.
One may be that common mode signals won't be present att the speaker terminals at all. On a "normal" balanced "dual amp", a common mode signal will indeed be present at the terminals, but in phase with each other so that no current will flow through the speakers.
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Hi... Any solution for this fault ? i got the same. Alle caps are change but not the main caps 10.000uF
this thread I have found today:
https://www.boomboxery.com/forum/threads/thule-spirit-ia-150b.30120/
https://www.boomboxery.com/forum/threads/thule-spirit-ia-150b.30120/