Hearing is believing...Redux!!!

steveinaz

Try contacting Parasound.

SCompRacer

Here is an older thread at Audiokarma that has some info. Post 18.

http://audiokarma.org/forums/index.php?threads/parasound-hca-1500a-strange-noise.345325/

txcoastal1

^^^^^Good info

Manti, make sure you give that info to any tech you use

txcoastal1

Parasound HCA 1500a schematic attached

Manticore

SCompRacer wrote: »

Here is an older thread at Audiokarma that has some info. Post 18.

http://audiokarma.org/forums/index.php?threads/parasound-hca-1500a-strange-noise.345325/

I think you hit one right out of the park!! This was just the info I needed. Thank You.

This info has been saved on my end.

For what I had noticed, the pots labeled TVR101 & TVR201 were the only two adjustable pots that I could find on the main board. I did not remove or disassemble the amp while looking. It was just a casual look & see.

Now that I know the values I will check the cool side value against the warmer/hotter side and see what the readings are; before I change anything. If the cool side is @ 10mV or very close I will know what to do.

Of course after spending several hours working in the backyard today... this will wait until at least tomorrow. I am absolutely whipped!

Thanks you all.

Manticore

txcoastal1 wrote: »

Parasound HCA 1500a schematic attached

Much appreciated. Filed.

SCompRacer

Happy to help. I see plenty of .33 ohm resistors they speak of. I guess measure across any one of them. R127 through R132 are left channel emitter resistors. Says right channel same as left or are they R227 - R232?.

Manticore

SCompRacer wrote: »

Happy to help. I see plenty of .33 ohm resistors they speak of. I guess measure across any one of them. R127 through R132 are left channel emitter resistors. Says right channel same as left or are they R227 - R232?.

Thanks for your time in helping with my amp problem. I will know more when I pop off the top and have another look see. According to that post #18 he states
" Tech support told me to test across .33 ohm emitter resistors".

I would do just that. Test across them all. Not sure if its necessary but, will give it a try hopefully later today or tonight. Time permitting. So much to do on my sprawling estate, (yeah right...sprawling). If I don't do it...

Spring and fall is the most work around the property. Have to keep the love of my life happy...





and my wife too.

Manticore

Ok well here are the results. After a 15 min or so warm up I checked the readings. The bias was off on both channels.
The left side read @ 7.1mV and the right side a whopping 21mV. It should be 10mV.
I am not sure why this was except for possible old age, or from shipping gentleness
(pun intended).

I took the readings off of R132 & R232 resistors as these were the most accessible for my somewhat sausage fingers. Although I wanted to take multiple readings from other resistors in the same line I chose not to.

The only two adjustable pots (that I could see) TVR101 & TVR201 both seem to be suffering from old age. They are very, very sensitive to adjustment. Just a fraction of a turn sent the reading from lets say 7.1mV to 32.0mV instantly. Maybe some corrosion on the contacts or maybe that's just the way they are. I don't know if I could have used some deoxit on them? Is there a certain type safe for circuit boards? If so I will order some. Maybe a project for another time.

Now they are both set @10mV with just a slight flutter up to 10.1mV every now and then.
I gave it a workout tonight listening to Stan Kenton Plays Chicago. Very impressive sound. I listened at just a slightly higher volume than normal and after all was done the amp was barely warm on both sides. It never broke a sweat.

This turned out to be a very simple adjustment because of the help from this forums members. Thank you all for your input and patience.

txcoastal1

Man that's awesome even saved the trip and expense to the doctor

Education for all included

Happy listening

tonyb

That info Rich posted was obviously helpful, glad you got the amp to where it should be. That will certainly improve the sound and it's life cycle.

Manticore

txcoastal1 wrote: »

Man that's awesome even saved the trip and expense to the doctor

Education for all included

Happy listening

Thanks for the schematic and yes its nice to save a buck or two. Eventually this unit will be sent out for a refresh.

tonyb wrote: »

That info Rich posted was obviously helpful, glad you got the amp to where it should be. That will certainly improve the sound and it's life cycle.

The info from Rich was the only reason this was able to be done. Thanks Rich

Funny you say that about the sound. I thought is was only wishful thinking but, it did sound better. I guess it shows one should trust their ears...most of the time.

tonyb

Manticore wrote: »

Funny you say that about the sound. I thought is was only wishful thinking but, it did sound better. I guess it shows one should trust their ears...most of the time.

Won't get an argument from anyone about trusting your ears. Even though mine isn't all that great, I can still pick out the sound of an Espresso being made from like 2.5 miles away.

Manticore

[/quote]

I can still pick out the sound of an Espresso being made from like 2.5 miles away. [/quote]

/\/\/\I should have added, send a box of Cannoli's with every speaker purchase, as long as we get to choose where they come from.

Sounds great. I still have not found a decent cannoli anywhere near where I live,
Or a good bakery,
Or good pizza,
Or good... well... just about anything worth raving about food wise.

steveinaz

I was gonna say, the adjusting points are hyper sensitive--but I see you got it.

motorhead43026

I also adjusted the bias on my 1500 last night, very simple process. The bias was really off both channels. I was really surprised the difference it made.

Manticore

steveinaz wrote: »

I was gonna say, the adjusting points are hyper sensitive--but I see you got it.

As they say up here in New England (wicked) sensitive. Man I dislike that saying.
But when in Rome...

After I noticed how sensitive the pots were I worked them back and forth a bit with the power off to see if I could work out any corrosion or whatever. I am going to check the readings again in a week or so to see if the settings stayed about 10mV.

Steve I think you said you had to or were going to do yours when you have some free time. I would be curious to hear if yours were way off or not.

Manticore

motorhead43026 wrote: »

I also adjusted the bias on my 1500 last night, very simple process. The bias was really off both channels. I was really surprised the difference it made.

OK this is starting to look like the norm. The difference was noticeable. I am very glad to be able to do this myself.

This makes me curious if the signal changed where I would have to rerun audyssey.

When listening in two channel I use the direct setting so there would be no change but for HT I use the room correction.