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Old 11th Apr 2011, 6:27 am   #21
Trevor
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Default Re: HH TPA series Power Amplifiers.

lets have the dc 300 story
regards trev
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Old 11th Apr 2011, 10:21 am   #22
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Default Re: HH TPA series Power Amplifiers.

'Scuse me butting in, but I remember reading some HH amps were loosely based on the Crown circuit. Being an owner of three D-60's (two bridged and one for headphone use) I can't believe how good they still are, 10% resistors and all (and then expensive 1% ones in the local feedback loops).

In domestic use, these amps can sound a touch lean and dry, due I suspect to their superior damping factor compared to the often sloppy domestic amps where bass-slop equates to "more bass...."

Hope you get them sorted.
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Old 11th Apr 2011, 11:19 am   #23
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Default Re: HH TPA series Power Amplifiers.

Also being a DC300A owner and user that would be of interest to me.
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Old 11th Apr 2011, 3:36 pm   #24
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Default Re: HH TPA series Power Amplifiers.

Hi everyone. Re the DC 300 A story, I know just how DC they can be in a fault condition. I was given one which was putting out around 60v dc on both channels and had fried the speakers connected at the time. I spent evenings in the shed checking for shorted devices but nothing obvious. I would leave it for days and come back to it but the dc was there as soon as it powered up. I found the CROWN AUDIO site and downloaded the 70 page manual. The fault I had was not mentioned as surely you would only expect one channel to be faulty and not both. I removed output devices and checked diodes then the drivers but I was still getting nowhere. It bothered me that having it powered up in this condition might be causing more damage. Then I had one of those light bulb moments! The amp I have has LED clip lights on the front panel marked IOC (input output comparator). It couldn't be something to do with that could it I thought? These are driven by a chip and four transistors and this gets its signal after the first stage pre amp chip. I pulled out the chip, powered up the amp and there was no DC on the output. Although now working I went on to find a couple of small transistors reading wrong and an o/c zener feeding the pre amp chip. I sourced the parts from DALBANI components (very helpful) and left the amp cooking dummy loads for a few evenings. Then I noticed the output of one channel lowering in output ( I had meters connected measuring volts ac). When checking I had around 8v dc on this channel. Now this was only happening as the amp warmed up. The manual says to check for leaky caps and has a basic but useful tip of holding a soldering iron close to any suspects. I had a rough idea where to start and after leaving the amp to cool, I powered up and watched the meter as I held the iron near an 82pf cap. Up came the voltage to around 8v. I removed the cap and the amp worked as normal.
Now here's the question, would this leaky cap have been the start of all the faults? It is close to the pre amp and the related problems initialy. I never bothered to try the LED clip lights again although I have got a new chip for that part.
Any similar stories anyone?
I have the 150 pre amp as well. It needed the 4 tantalum caps changing to get it right. The manual mentions those.

David.
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Old 11th Apr 2011, 6:17 pm   #25
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Default Re: HH TPA series Power Amplifiers.

Mine are working ok atm but I should really give them a check over. I did replace the op amps in the pre-amp with a recommended later type though.
The DC300A is legendary with many stories about their ruggedness. The best IMHO is the rumour that they will happily function as an arc welder with DC fed to the input !
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Old 11th Apr 2011, 7:22 pm   #26
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Default Re: HH TPA series Power Amplifiers.

Hi David as per PM here are a few picture of the TPA50 kindly donated to me by robin0755. Not applied power yet my ESR meter absent without leave!. Basic checks don't reveal any shorts so may just power via limiter mid week when I have more time. I have sorry borrowed some dummy loads just in case, don't want the Radfords to get zapped Have fun Mike T
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Old 11th Apr 2011, 9:31 pm   #27
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Default Re: HH TPA series Power Amplifiers.

Quote:
Originally Posted by teetoon View Post
I have the 150 pre amp as well. It needed the 4 tantalum caps changing to get it right. The manual mentions those.
Sounds like a later DC300A?
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Old 11th Apr 2011, 10:06 pm   #28
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Default Re: HH TPA series Power Amplifiers.

cobalt blue are you in a posistion to tell us what the output transistor are ? i can see no driver transistors on your photo,s
regards trev
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Old 11th Apr 2011, 10:12 pm   #29
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Default Re: HH TPA series Power Amplifiers.

Hi Trev yes they are darlingtons MJ4032 and MJ4035 best regards Mike T
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Old 11th Apr 2011, 10:35 pm   #30
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Default Re: HH TPA series Power Amplifiers.

Hi Mike, That is a much later 50 D you have there. I would just power it up without a speaker connected. If you have a meter there just chack for dc on the output. There should be no more than + or - 100mv. You could have a look at the front panel fuses to make sure they are intact and of the correct rating first. I reckon it will be fine though. Those XLR mains connectors are a pain and best changed or even hard wired. The input transformers are very good but can be bypassed if your really critical. I personally can't hear any difference having them in circuit.
I've posted a couple of blurry pics of the boards on my 50 D's. You can read the board numbers and see the different layouts. The late amps like yours had much thicker wiring too. I have a 100 D that looks like your amp. I think these must have been early 80's. I'm sure the smoothing caps in mine are dated 82.

D S J R,
The IC 150 I mentioned with the tantalum caps, they are 1 mfd and are very distinguishable from their red and black ends. You can download manuals from crownaudio.com for free.

David.
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Old 11th Apr 2011, 10:54 pm   #31
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Default Re: HH TPA series Power Amplifiers.

Hi David the caps are dated 83 week 7 so you are spot on with the date I have the right XLRs so I think I will keep them for now fortunately no tants in sight!. Undecided about the transformer but I have some 9 pin plugs from Anita calculators destroyed in the 70's so I can soon bridge it out. Thanks for all your help to date, Now I just need to find another one. Mike T
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Old 11th Apr 2011, 11:36 pm   #32
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Default Re: HH TPA series Power Amplifiers.

Hi again, some pics of the early 80's 100 D. Well actually it's just called a TPA 100 on the back plate, but this is just confusing.
Mike, if you read the back left hand side model number,it should say the power output into 4 ohms. What does it say?

Trev, notice the much thicker wiring on this one and dig the go-faster red heat sinks!

David.
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Old 12th Apr 2011, 7:36 am   #33
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Default Re: HH TPA series Power Amplifiers.

Hi David Likewise no mention of D on the backplate it says 100W / 4Ohms
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Old 12th Apr 2011, 5:56 pm   #34
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Default Re: HH TPA series Power Amplifiers.

Thanks for that Mike, you'll have to keep an eye out for a matching one now.
Have you plugged it in yet?
Although I drifted slightly ot with the DC 300 A bit, there is a connection to HH there. It seems HH copied a lot of the Crown circuit for the S 500 D. It had very similar specs when introduced in the mid 70's. They sounded great and the styling was very smart compared to the Crown's.
Anyone done anything with Carver amps? I've got a smoked PM 350.

David.
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Old 12th Apr 2011, 8:24 pm   #35
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Default Re: HH TPA series Power Amplifiers.

At last I have worked out the protection circuit so will shortly post the schematic for the 100 amplifier what strange thinking? re the design
All in all a super design if you require high reliability etc
Teetune due to the fact that I am reluctant to take apart the amplifiers have and that you have a stripped down one can you advise me what the to66 driver transistors are on the heatsinks
regards Trev
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Old 12th Apr 2011, 8:32 pm   #36
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Default Re: HH TPA series Power Amplifiers.

Unfortunately not had the time to power up yet too many projects on the go at the moment. Should be next week.
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Old 13th Apr 2011, 12:00 am   #37
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Default Re: HH TPA series Power Amplifiers.

Hi Trevor, the drivers on the heat sinks are 2N3441. It makes me wonder what the max output is as there are only 2 output devices where as, the D version has 4. The power supply is the same size in both versions.
Yeah they certainly were built for reliability. A lot were used by TV and Radio companies for monitoring duties and the few studio's I've seen tend to leave the equipment on 24/7. There's evidence of this above the wirewound resistors with the sooty marks on the lids! Those amps did smell nice when running in my shed. Have you sussed the distortion problem with them? Also, what do you think of the preamps? I'd love to know who made them and why.

David.
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Old 13th Apr 2011, 7:32 pm   #38
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Default Re: HH TPA series Power Amplifiers.

Hi David, good news. I finished early so I had time to power amp before I got stuck into the rest. DC offset on the output is just 26mV. The supplies on the reservoir caps +/- 47.5V. I did a quick crude test with speaker and CD player and all seems OK. Neighbours not too impressed. I will run it up with sig gen and dummy load next week. But seems as if I have nothing to do but enjoy. and off course search for another one. Wish I could say the same of the Tangent Lupus Princeps looks like I will have to chuck a whole bag of caps at that. Now I must get back to my Philips Videodisc player. Its started jumping its not the discs as they play OK on my other VLP600 (that ones in Exeter). Thanks for all your assistance to date Have fun Mike T
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Old 13th Apr 2011, 8:58 pm   #39
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Default Re: HH TPA series Power Amplifiers.

The only HH amplifiers I remember were, I think, the IC series and the MA series in the early & mid seventies. They used to sound good and also looked good in the dark, with the green illumination around the controls. Lots of groups and a few discos round here used them. As I recall, the MA series had a "valve sound" option, presumably for guitarists.

I've got some brochures in the loft somewhere. They also did really nice looking speakers. I always thought thought that the amps used toroidal mains transformers, but perhaps they didn't.

Also, were Crown and Amcron the same company?

All the best

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Old 13th Apr 2011, 11:02 pm   #40
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Hi Aub, yes the IC 100 series were ground breaking amps back then. Much more reliable than some of the valve stuff that was used by groups of the time. I don't mean valve amps in general, it was everyone using old amps that had never been serviced and probably still had the original valves! I had a Selmer TnB 50 with a faulty treble channel (I played bass so didn't matter) and it never liked being on top of the speaker cab. After a summer season I bought an HH VS Bassamp. The VS meaning valve sound. It was just a type of harmonic distortion inducing pre amp, and you could buy a pedal with a picture of a valve on it just to switch the effect in! It was a good amp though and very reliable, even after being dropped a few times. The IC 100 amps, MA 100 (mixer amp) and S130 (slave amp) all used toroidal transformers.
Same on the valve sound range too.
Funnily enough, the green glow was how I found this forum. I had a S130 slave amp bought second hand in sept 2009 and the Electroluminescent front panel didn't work. I was doing a web search and came up with a result refering to a radio which used this technology around the dial I think? Anyway, like you do I hit the home page and discovered this excellent forum. Took me a while to join though.

Amcron was the name they made from The American Crown Company. Crown was already a registerd name in europe so they had to use something else. That's the gist of it anyway.

Mike, well done. I thought it would be OK. I play stuff like reggae and Boards Of Canada through mine in the shed! Great bass!
David.

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