Help Arcam Alpha 5+ spinning too fast HELP please

filholder · 20th April 2005, 07:51 PM

Hello

If anyone has any experience with these player please i need some help.

I have just changed various capacitors on the DAC board before and after regulation. This all went fine but when i put the player back together the CD started spinnign very fast. I took off the board and remounted it again in case something had not lined up but it keeps doing it.

All the caps were replaced with those of the same value and rating but just blackgates and elna. Have checked and all in the right position

Anyone got any ideas.

Beside myself

fil

TDA1540 · 20th April 2005, 09:35 PM

probably lost the 11MHz systemclock signal, running from the filter to the decoder.

filholder · 20th April 2005, 11:54 PM

Ok but how did i do that just replacing some caps?

Have checked everywhere and cant see a loose connection.
one thing i did notice was that when checking continuity aroundf the volatge regualtors. after testing 2 pins and then swapping over to another 2 pins the continuty tester bleeps for half a sec and then stops. Always does this. Is this normal or might it be faulty? It a LM337t.

Cheers

Fil

Extreme_Boky · 21st April 2005, 12:21 AM

Hi filholder,

How is the CD mechanism board connected to main PCB? Via ribbon cable / flexible membrane cable? You should check and make sure that all the pins are okay and that all make good connection. This can happen if you lost a clock signal, or feedback signal(s) for the servo control circuit. So, if you haven't touched the clock, check all connectors.

Good luck,
Extreme_Boky

apollyon25 · 21st April 2005, 12:24 AM

Off the top of my head...
This is most likely the internal series pass transistor, or the internal diode used to prevent output overvoltage spikes from killing the regulator - look up the datasheet...

Good luck

filholder · 21st April 2005, 09:43 AM

I think that the most likely issue is the regulators on the dac board.

One thing i did do was resolder the voltage regulators, all four of them, since had issue with them before. They are the highest things on the board with heat sink and tend to move when you work on the back side of the board. This has lifted the tracks on a couple but i have repair the track and get continuty fine now. I wonder if the repeat soldering in this area might have damaged them?
I am wondering if i might have damaged one. I was going to go to maplin today buy replacments and them swap them all.

"internal series pass transistor, or the internal diode used to prevent output overvoltage spikes from killing the regulato"

The 'internal diode' do you mean within the voltage regulator or somewhere else.

Fil

tubenut · 22nd April 2005, 10:24 AM

Check voltages on the regulators. If the 7220 does not get its required 5 V it will spin endlessly at high speed. Same as clock problem.... Also check the PSU feeding the clock cct, it probably has a 74**** something (18 pin IC I think) that also requires 5 V.

Changing caps should not cause this problem, but a bad solder job while doing the caps could be shorting a PSU. If you find this is the problem, check the regulator is still OK....

filholder · 24th April 2005, 07:57 PM

Sorry been away for 3 days back to the sticks for my mother birthday.

Anyway on with the testing.

I changed the voltage regulator which i had messed about with and got no luck.

Also i have checked the voltages going into the dac board and the +25v reads 27 V and the -25v reads -21v. Does that sound very wrong? Any idea

Sorry to plead ignorance but how do i test a diode? This relating to Q604 and Q605.

Cheers

Fil

juancho · 25th April 2005, 07:33 AM

Hi,
I got similar voltage readings on my DAC board and traced it to a blown FS 217 transistor. Replacing that quickly sorted things. However, that affected the section not the clock signal so doesn't explain your cd spinning too fast whih as others have said points to a fault with the clock signal.
David

filholder · 28th April 2005, 01:37 PM

All fixed now, the network of a diode and transistor between the 25v input and the first first plus voltage regulator(+15v) were blown and thus the reg wasnt getting voltage. And since the +5v reg gets its voltage from the +15vs output there was no + voltage on the board.

If this happens to anyone and from my amount of digging on forum it has happend to a few people then the diode to replace is a 2v7 and the transistor marked as a fst239 can be replaced by the far more common BC549C.

I feel this might have happened beacuse the caps store charge for a hell of a long time after switch off and when you seperate the main board and the audio board and tiny arc can occur. Thats my guess, so i discharge all the caps before seperating the boards now.

20th April 2005, 07:51 PM	#1
filholder diyAudio Member Join Date: Jan 2005 Location: london	Help Arcam Alpha 5+ spinning too fast HELP please Hello If anyone has any experience with these player please i need some help. I have just changed various capacitors on the DAC board before and after regulation. This all went fine but when i put the player back together the CD started spinnign very fast. I took off the board and remounted it again in case something had not lined up but it keeps doing it. All the caps were replaced with those of the same value and rating but just blackgates and elna. Have checked and all in the right position Anyone got any ideas. Beside myself fil

22nd April 2005, 10:24 AM	#7
tubenut diyAudio Member Join Date: Nov 2002 Location: South Africa, Jhb	Check PSU voltages Check voltages on the regulators. If the 7220 does not get its required 5 V it will spin endlessly at high speed. Same as clock problem.... Also check the PSU feeding the clock cct, it probably has a 74**** something (18 pin IC I think) that also requires 5 V. Changing caps should not cause this problem, but a bad solder job while doing the caps could be shorting a PSU. If you find this is the problem, check the regulator is still OK....

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20th April 2005, 09:35 PM	#2
TDA1540 diyAudio Member Join Date: Feb 2004 Location: Ehv	probably lost the 11MHz systemclock signal, running from the filter to the decoder.

20th April 2005, 11:54 PM	#3
filholder diyAudio Member Join Date: Jan 2005 Location: london	Ok but how did i do that just replacing some caps? Have checked everywhere and cant see a loose connection. one thing i did notice was that when checking continuity aroundf the volatge regualtors. after testing 2 pins and then swapping over to another 2 pins the continuty tester bleeps for half a sec and then stops. Always does this. Is this normal or might it be faulty? It a LM337t. Cheers Fil

21st April 2005, 12:21 AM	#4
Extreme_Boky diyAudio Member Join Date: Dec 2003 Location: Sydney	Hi filholder, How is the CD mechanism board connected to main PCB? Via ribbon cable / flexible membrane cable? You should check and make sure that all the pins are okay and that all make good connection. This can happen if you lost a clock signal, or feedback signal(s) for the servo control circuit. So, if you haven't touched the clock, check all connectors. Good luck, Extreme_Boky

21st April 2005, 12:24 AM	#5
apollyon25 diyAudio Member Join Date: Sep 2004 Location: Auckland, NZ	Off the top of my head... This is most likely the internal series pass transistor, or the internal diode used to prevent output overvoltage spikes from killing the regulator - look up the datasheet... Good luck

21st April 2005, 09:43 AM	#6
filholder diyAudio Member Join Date: Jan 2005 Location: london	I think that the most likely issue is the regulators on the dac board. One thing i did do was resolder the voltage regulators, all four of them, since had issue with them before. They are the highest things on the board with heat sink and tend to move when you work on the back side of the board. This has lifted the tracks on a couple but i have repair the track and get continuty fine now. I wonder if the repeat soldering in this area might have damaged them? I am wondering if i might have damaged one. I was going to go to maplin today buy replacments and them swap them all. "internal series pass transistor, or the internal diode used to prevent output overvoltage spikes from killing the regulato" The 'internal diode' do you mean within the voltage regulator or somewhere else. Fil

24th April 2005, 07:57 PM	#8
filholder diyAudio Member Join Date: Jan 2005 Location: london	Sorry been away for 3 days back to the sticks for my mother birthday. Anyway on with the testing. I changed the voltage regulator which i had messed about with and got no luck. Also i have checked the voltages going into the dac board and the +25v reads 27 V and the -25v reads -21v. Does that sound very wrong? Any idea Sorry to plead ignorance but how do i test a diode? This relating to Q604 and Q605. Cheers Fil

25th April 2005, 07:33 AM	#9
juancho diyAudio Member Join Date: Apr 2005 Location: East Sussex, England	Hi, I got similar voltage readings on my DAC board and traced it to a blown FS 217 transistor. Replacing that quickly sorted things. However, that affected the section not the clock signal so doesn't explain your cd spinning too fast whih as others have said points to a fault with the clock signal. David

28th April 2005, 01:37 PM	#10
filholder diyAudio Member Join Date: Jan 2005 Location: london	All fixed now, the network of a diode and transistor between the 25v input and the first first plus voltage regulator(+15v) were blown and thus the reg wasnt getting voltage. And since the +5v reg gets its voltage from the +15vs output there was no + voltage on the board. If this happens to anyone and from my amount of digging on forum it has happend to a few people then the diode to replace is a 2v7 and the transistor marked as a fst239 can be replaced by the far more common BC549C. I feel this might have happened beacuse the caps store charge for a hell of a long time after switch off and when you seperate the main board and the audio board and tiny arc can occur. Thats my guess, so i discharge all the caps before seperating the boards now.

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