Vintage Products

Re: Beolab Penta with some scratches

mhw — Tue, 12 Apr 2011 13:49:58 GMT

Thank you very much for the help!

The Beomaster have not been serviced, so it's probably something dodgy there. It pops when I turn it on from cold aswell, so I guess it's about time to have it serviced!

About the Penta: It's definitely not the cable; I plugged it out and tried with a line source, and it's still there. It reminds me of the sound from high voltage lines and it's coming from the amp itself, so my guess is the transformer... I will bring it to the shop tomorrow!

Re: Beolab Penta with some scratches

Premiumverum — Tue, 05 Apr 2011 03:07:32 GMT

Very good!

The thump seems to be coming from the beomaster, have you had that recapped/serviced too?

Just went over all the replies again, concerning the buzzing: have you already checked it is not from the cable, by swapping the powerlink from the left and right speaker?

Re: Beolab Penta with some scratches

mhw — Mon, 04 Apr 2011 16:09:56 GMT

Just an temporary update if somebody finds this thread in search of help with similar problems:

The MMC came back from Axel working as it should and is now sounding very good!

The Penta amps came back from the shop today, after a full recap (Martin's kit) and supposedly re-soldering any bad solder joints. They sound very good! But it did not fix the buzzing problem - it's still there, maybe a little quieter, but still annoying.

The thump is still there, and seems to get louder if I have more stuff plugged in to the Beomaster (with only one speaker and my iPhone plugged in, it's barely audible, but with all the other stuff plugged in it's quite loud).

I will report back when/if I find out more!

Re: Beolab Penta with some scratches

mhw — Sun, 20 Feb 2011 14:33:38 GMT

Finally checked it out some more tonight: The thump from the lights is not there when the speakers are in LINE mode (and switched on), BUT when I connect some chep computers speakers to the Beomasters headphone socket they make the same noise... Sounds like the Beomaster may need some work too!

Re: Beolab Penta with some scratches

mhw — Thu, 17 Feb 2011 12:36:35 GMT

I'm pretty certain that the buzzing is from the amp itself, and not the speaker elements... And it's still there in LINE mode!

I will check if the thump from the lights are still there in LINE mode tonight!

Re: Beolab Penta with some scratches

lausvi — Thu, 17 Feb 2011 11:16:21 GMT

My Penas had new caps and the update Martin mentioned. Both of the speakers have a faint buzz when they are on. The distance to the listening place is about 2m and I can hear the buzz there (very faint and easily lost in music but still) - is this normal or is there still something funny going on? The cables I got with the speakers, they are self-made but look-and-feel pretty solid, I checked the solderings on both ends. Source is my Beocenter 9000. Perhaps I should try the RCA-shorting -trick to see what happens.

Also one of the speakers makes an audible pop when it switches off, the other one doesn't.

Re: Beolab Penta with some scratches

Dillen — Thu, 17 Feb 2011 08:46:37 GMT

Another thing is that not all link cables are equally good.
Some cables will introduce a background buzzing from the speaker.
Often, the amplifier (which works at full volume all the time) will also produce a buzz
if no signal cable is attached.
If in doubt, pull out the signal (link-)cables and insert an RCA plug that you can short.
If the buzzing disappears when the RCA plug is shorted, the problem is not in the amplifier.

Martin

Re: Beolab Penta with some scratches

Dillen — Thu, 17 Feb 2011 06:55:11 GMT

Capacitors, yes.
The Pentas are not as old as most other B&O's with capacitor problems but the
majority of capacitors used in the Pentas are 85deg types and since they work in a
warm environment, they don't last very long.
The available capacitor kits contains 105deg capacitors with a slightly higher voltage
rating in selected areas (power supply) so should last a lot longer.
The kit also contains the upgrade (originally suggested by Die_Bogener), consisting of WIMA MKS-2
foil caps and Burr-Brown Opamps in the preamplifier signal paths.

The best places to find cracked solder joints in the Penta amplifier is at the
driver transistors and the long row of solder joints at the front, next to the front panel connector
(I don't remember what it connects to).

Martin

Re: Beolab Penta with some scratches

mhw — Thu, 17 Feb 2011 06:16:15 GMT

Premiumverum:

mhw:
Thought that was more like a hum than a buzz? And the amp doesn't get very warm...

That is true of course, but the pop when switching lights made me think the PSU capacitors don't have a lot of reserve left. Anyway, a recap is never a bad idea, how old are the pentas?

Another possibility: a bad solder joint or connection somewhere that starts acting up when the amp gets hot. Bad joints are pretty common in pentas I believe!

Maybe Dillen can shine his light on this case?

I was hoping he would

They're from 1998, so not the oldes pair around...

Re: Beolab Penta with some scratches

Premiumverum — Thu, 17 Feb 2011 05:54:58 GMT

mhw:
Thought that was more like a hum than a buzz? And the amp doesn't get very warm...

That is true of course, but the pop when switching lights made me think the PSU capacitors don't have a lot of reserve left. Anyway, a recap is never a bad idea, how old are the pentas?

Another possibility: a bad solder joint or connection somewhere that starts acting up when the amp gets hot. Bad joints are pretty common in pentas I believe!

Maybe Dillen can shine his light on this case?

Re: Beolab Penta with some scratches

mhw — Wed, 16 Feb 2011 15:47:48 GMT

Premiumverum:

I think you should get those pentas recapped and readjusted! I remember seeing pictures here of a near exploded penta amp power supply that had a buzz and the owner had just kept using it. Your buzz and the pop when you use the light might indicate a PSU running on its last bit of legs. Maybe Dillen can supply a capacitor kit?

A recap will improve sound too by the way, especially if you do some mods that are suggested here (search for penta high end or something)

http://forum.beoworld.org/forums/p/14509/111394.aspx

Thought that was more like a hum than a buzz? And the amp doesn't get very warm... But I guess it's a good idea non the less - I will contact Dillen! Thanks!

And thanks to you too mediabobny - I will send it to Axel!

Re: Beolab Penta with some scratches

mediabobny — Wed, 16 Feb 2011 15:06:52 GMT

Yep; typical suspension degradation problem. Either Axel or Sound-Smith can rebuild it, with Axel being less costly.

Re: Beolab Penta with some scratches

Premiumverum — Wed, 16 Feb 2011 15:04:55 GMT

I think you should get those pentas recapped and readjusted! I remember seeing pictures here of a near exploded penta amp power supply that had a buzz and the owner had just kept using it. Your buzz and the pop when you use the light might indicate a PSU running on its last bit of legs. Maybe Dillen can supply a capacitor kit?

A recap will improve sound too by the way, especially if you do some mods that are suggested here (search for penta high end or something)

http://forum.beoworld.org/forums/p/14509/111394.aspx

Re: Beolab Penta with some scratches

mhw — Wed, 16 Feb 2011 14:37:21 GMT

Thank you very much! I have ordered a new top panel (or I think so, these B&O dealers aren't very fast to respond to emails!).

One more quick question; I think the MMC2 on my Beogram 7000 have seen better days. When it's at its recommended stylus pressure, I have to have my finger on it for the sound to be good. When I turn up the stylus pressure it is enough for me to just touch it once and the sounds becomes good. I'm guessing it's time for a trip to Axel at Schallplattennadeln?

I will surely come back with more questions later when I have more time, because the bzzzing is very annoying when playing movies or listening to quiet music and the speakers "pop" when I turn off the lights in another room!

Re: Beolab Penta with some scratches

joeyboygolf — Tue, 08 Feb 2011 13:09:18 GMT

mhw:

One of the top panels got a dent in transit though, but that's life I guess...

You can still order these from your B&O dealer