ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
I visited a strange store today - it was stuffed with items for "collectors". There were thousands of records, post cards, stamps, envelopes, photos, toys and a lot of other old junk. I went there for the records mostly; but he had just received a cute (well, for it's size....) B&O Grand Prix Moderne 610 K from 1964 with Type M speakers... Working condition, lights up. Magic eye tube finding stations and speaker static noise. I'll think about it!
I hurried down the store this noon to buy it before anybody else! Took it to my workshop and had a look at it; FM works - no stereo module unfortunately, Tape inputs are weak, Phono works, treble control is stuck, other buttons are working fine. Nice valve sound!It needs cleanup and some oil to the beautiful rosewood cabinet. it is going to be used with my S75 speakers when I get it repaired.
The reel deck in the background is a big Fostex 16 track 1/2" recorder which is huge, the receiver is bigger than it seems!
Vinyl records, cassettes, open reel, valve amplifiers and film photography.
Nice find Soren . I will not ask where its going. :-0
Valves... I love valves! I want that receiver now. Well done, as usual...
Jacques
Nice piece and it seems to be in excellent condition.However, Beovox S75 won't be a very good match for a valve amplifier. Their impedance is far too high.
Use the type M speakers, their impedance is 3,5 ohms and an exact match (surprise ).
Martin
Nice piece Søren, keep us informed on progress, maybe Martin can help with a stereo decoder, The wood looks beautiful, I love to see how they always made each box out of one piece of veneer,
Collecting Vintage B&O is not a hobby, its a lifestyle.
That is certainly a nice radio.
I have a Grand Prix Present 610K, which has built-in speakers, too. Lovely sound! It has a small crackling sound on one channel. I did a complete re-cap (with a kit from Martin) but it's still there, haven't had time to have a better look on what's causing it.
From the second picture it looks like yours still has the original envelope with the schematics, too. I even got a danish user manual with my set. It's available here (Beoworld manuals section).
Nice workbench, too.
lausvi: a small crackling sound on one channel
a small crackling sound on one channel
Usually a valve pin/socket intermittent contact. If only in one channel it would most likely be in the amplifier stages.Could also be a bad switch contact but that will normally be easily diagnosed by operating the switches.
Thanks Eddie - I have thought about the late B&O valve sets for a little while; I sold off three Beocord 8000-series decks yesterday and a Denon cassette deck tomorrow which means that I have more vacant space than wanted
Thanks Chartz, I know why you like the old models - a whole other (but excellent) feel and very high build quality. I really have to get a quartet of NOS PLC84 valves to get it to chime...
It's really beautiful, Martin. A few dents and scratches, but it's in very good nick considering that it is turning 50 next year. The front panel is intact with the lettering, knobs are not miscoloured and the set has apparently been owned by non-smokers which is pretty impressive because most Danes were regular smokers in the 1960's. I thought that the impedance may be wrong with the S75's. 4 Ohm speakers may suit better as they are in the 3-5 ohm range; the Type M speakers are lifeless and dull in my opinion, and they can't handle sound pressures higher than half turned up on the volume knob. I seem to remember that they were rated at about 5 watts?
Hmm... I think that the stereo decoder module was solid-state. Maybe it was identical to the Beomaster 900 module? My Granddad bought a 900 when new and had it fitted back then.
Ahh, It was your manual I read earlier today, Lausvi (nice avatar, BTW)! Thanks for uploading it as I was in doubt concerning the speaker selector switches as I was afraid that I may damage something if the speakers were left unconnected because of wrong switch position.
By the way, there seems to be a layer of yellow dust all over the chassis. Does anyone know what it is? The consistency is the same as corn starch.
A great find!
When this set came out, it was very early days for FM stereo, and the system used for transmission wasn't even agreed upon yet. Even though it is "stereo ready", it might need a number of modifications in the IF stages and the detector to pass the entire audio bandwidth needed for the stereo system that eventually ended up being selected (and is still used today). Beomaster 900 is just the critical couple of years younger in design that installing the MPX decoder is (mostly) just a plug-in job.
--mika
The yellow "dust" is very common. It's the result of airs moisture reacting with thesurface treatment (tin or nickel) of the chassis metal.Nothing to worry about.
The stereo decoder will be very difficult to find and, as Mika suggests, not easily installed.
It's correct that the sound reproduction of the Grand Prix depends greatly on the speakers.It's a very high quality set with a wonderful sound and the Type M speakers, that were immensely popularat their time, may not be the best.Try to find a pair of Type S speakers or even K, they are both fairly rare compared to the Type M but will sound better,while still maintaining a reasonable design match.
Aha, I thought it had a metallic smell to it
Hmm, I'm re-reading through the restoration thread on the archived forum (I love to read your restoration threads, will there be more in the near future?) which does make it seem very difficult to install and find - could be nice to have though.
I have heard a pair of Type K speakers which sounded fantastic, that large volume enclosure really does something good for the bass response.
I could imagine that this set was the most luxurious radio available back then, it easily compares with the Beomaster 8000 when looking at average specifications of their time. 15 W per channel is quite a lot, 11 valves, an awesome AFC circuit and so forth did make it superior to other Danish sets of the age. I have read that the input board was a standard BOFA board - is that true?
Started cleaning the valve sockets and pins today with contact cleaner (funny, it smells like "Jenka" chewing gum) - all valves are Philips Miniwatt except the ECC85 which is a Siemens, they are original as they all has a B&O date stamp - April 1963. The enclosure is from August 1963, and the little envelope contained the diagram
The valves were wiped on a wet towel to remove fifty years of burned dust - just to dampen the smell of hot dusty electronics in my room at home.
Beautifully made...
The valve cleaning made the last crackle disappear and FM tuning was far better - still changing the ECC85 and maybe the two ECC83's as I have some NOS Siemens tubes laying around. I found out that there was some corrosion around the same fuse (at the ferrite antenna) that Martin had experienced with his Grand Prix 609. It was not that bad, the fuse holder was still mechanically strong and sound. Sanded off the corrosion and installed a cleaned fuse.
The knobs were taken off and cleaned in an ultrasonic cleaner using soapy water, it came out beautifully. Before:
and after:
A pleasure to see this. Good job !And thanks for the comment higher up . Yes, I'm still doing some write-ups, just not posting much at present .
Dillen: A pleasure to see this. Good job !And thanks for the comment higher up . Yes, I'm still doing some write-ups, just not posting much at present . Martin
Søren you are agitating my BeoVirus, I have been thinking about where to go after finishing my BM 4400, the house is full with B&O, but a valve radio is a must, over here they are very rare, so a DK trip this summer is in the planning phase. I have to go anyway as I owe Martin a couple of beers.
Nice thread Søren, who needs Martin
I know that I am doing it right when the Beomeister himself likes it
You're welcome, your restoration threads are a pleasure to read.
Well... Got the receiver home and tried it on my MS150.2's (I know they are far too big to be driven well)... Awesome... I like how the dial lights up.
Beautiful pics, just a side remark, a little motor oil, on a rag to the galvanized chassis parts and covers will protect against further oxidation, and give them a fresher look.
Useful advice, Søren
I think I need to replace some capacitors in the tone shaping circuits. Does anybody have an idea to get a stuck potentiometer to move again?
Søren Hammer: Does anybody have an idea to get a stuck potentiometer to move again?
Does anybody have an idea to get a stuck potentiometer to move again?
Most likely seized where the potentiometer spindle passes through the potentiometer housing.Let it soak a day or two with a drop of sewing machine oil. Work it carefully with pliers every now and thenand it will usually start moving little by little.When it's freed completely, add another drop of oil and it'll be fine for many years to come.Remember to do the same with the other potentiometers or they will eventually become stuck too.DON'T get any oil on the plastic knobs, they will become incredibly brittle and fall apart at the slightest touch.
Thanks Martin - Acid free oil really can do wonders. The knobs are far to rare to risk anything, especially because these are the 1964 ones which were used on only a few other B&O products because they changed over to metal knobs.
I have been listening for a couple of hours and I seem to receive a lot of FM stations, hot valves really makes it sensitive. Do you know if the set applies plate voltage to the ECC85 when FM isn't selected?
The clean-up on the buttons was impressive!
Søren Hammer: Ahh, It was your manual I read earlier today, Lausvi (nice avatar, BTW)! Thanks for uploading it as I was in doubt concerning the speaker selector switches as I was afraid that I may damage something if the speakers were left unconnected because of wrong switch position.
Avatar; thanks First to comment on that!Great that somebody uses that manual I scanned, it's not too easy to find from the manuals section, especially if you look for just for the model you have.
I was thinking about the FM decoder. I looked thrue my photos re-capping my 610K some two years ago. The FM-module is a separate module and it does have a connector that connects to a plug on the top of the chassis, as here:
Note that there is a stamped date next to the schematic pocket. I think it reads 23 SEP 1969, which could a date of when the decoder was installed.
Søren: looking at your photos, I think there is similar plug installed in your radio as well. I would believe that indicates that the set is at least prepared for the FM-Stereo reception. Finding one of those modules might be more of a challenge!
Reading this thread makes me hope I'd have a time to have another look on my 610K. At the moment it's sitting on a top of a shelf at work, where I don't think its going to see too much action.
And yes, we all love those parts-glowing-in-the-dark photos. The scale-lamps are awesome. Here is one with the valves shown.
And one more photo...
Your Grand Prix is beautiful... I can't get enough glow-footage. Are all your valves original?
This picture reveals that my set is prepared for a decoder. It sure could be nice if the circuit for it could be found, or at least backward engineered.
I am trying out the AM section now, picking up loads of stations, 1269 kHz from Neumünster plays classic rock at the moment!
I wish I had a better camera for low-light photographing, all I have at the moment is my Samsung Galaxy SIII which is excellent for normal light conditions.
Edit: Found a picture from earlier today.