Brenell Mk5 M - UK Vintage Radio Repair and Restoration Discussion Forum

Earczar · 2nd Nov 2018, 8:22 pm

Hi everyone this is my first post, im looking for some help trying to identify where a few components that need to be re-soldered. It took a long journey to Canada from the UK, so i hardly blame it letting go. It seems untouched but who knows? Im going to do a full recap eventually but want to have it in order first. The first resistor is 180kohm and the second says 350pF. The 350 has a flat connection so it should have been easy to spot but im totally stumped. Also they are both connected to the middle wafer.

wd40addict · 5th Nov 2018, 2:27 pm

These values don't correspond to anything I can find on the schematics. What is the function of the switch they connect to?

If you've imported the machine from the UK I assume you know the speed will be wrong unless it's a 60Hz version?

Earczar · 5th Nov 2018, 4:35 pm

I thought the same thing with the values. After seeing other pictures this one must be modified. The heads are not that fantastic, i think ill strip it down and rebuild it as a preamp. The switch that they are on is to change the speed. Theres other loose connection i cant trace as well. I took a chance and unfortunately this will be a bigger project then expected. I do have a step up transformer but that wont solve my speed problem right? Unless i just run it at 11.75 ips or whatever it will roll at and only playback on same deck.

rontech · 5th Nov 2018, 7:28 pm

I had a Brenell Mk 5 in the early 1960's I seem to remember the capstan sleeve was brass and removeable, with the large one for 3.5, 7, 15 i.p.s and a smaller one for 1 7/8 3.5 and 7 i.ps.

If you know somebody with a good precision lathe, then suitable diameter capstans in brass may correct for the difference 60 hz / 50 Hz.

vidjoman · 5th Nov 2018, 8:53 pm

They were available in those days direct from Brenell, so easy to replicate.
The switch you referred to changes the equalisation of the amplifier to suit the ‘speed’ of the deck. It doesn’t change the speed, which is on the main deck.

Earczar · 5th Nov 2018, 10:35 pm

I have both speed sleeves. Anyone know the size to replicate a 60hrtz motor.
And yes they are definitely brass. Its possible i could get someone i used to work with to fix it on the lathe. Im starting to feel hope again on this deck.
Thanks everyone for the advice.

rontech · 6th Nov 2018, 10:02 am

I imagine that a 50Hz motor will run fast by 6/5 (i.e. x 1.2 ) on North American 60 Hz supply. The tape speed will be defined by capstan circumferences per second. (pi x d) i.ps. where d is capstan diameter in inches. pi = 3.142 for practical purposes.

I think the above is correct; it is 60 yrs since passing my 6th form math's exam.

Stevie342000 · 6th Nov 2018, 10:40 am

If I recall correctly the standard size of the capstan sleeves is 1/2" and 1". You could always measure them with calipers.

lesmw0sec · 6th Nov 2018, 11:12 am

Quote:

Originally Posted by rontech

I had a Brenell Mk 5 in the early 1960's I seem to remember the capstan sleeve was brass and removeable, with the large one for 3.5, 7, 15 i.p.s and a smaller one for 1 7/8 3.5 and 7 i.ps.

If you know somebody with a good precision lathe, then suitable diameter capstans in brass may correct for the difference 60 hz / 50 Hz.

The first passable tape deck I bought was a Collaro Studio and I recall fitting a capstan sleeve so it could run at 15 ips.

Earczar · 6th Nov 2018, 11:26 am

I'll deffinately measure them up with calipers, they look close to 1/2 and 1". Thanks for the math lesson Rontech. This is my first over the pond attempt if that is not already clearly obvious....lol

vidjoman · 6th Nov 2018, 11:34 am

I would suggest that you keep the originals and get new ones made. You’ll have the originals for reference.

wd40addict · 6th Nov 2018, 2:14 pm

My small capstan was slightly under 0.5", about 0.495" from memory, but my machine has the Pabst motor. It's possible the earlier AEI based models had the slightly larger diameter as I don't believe that motor was fully synchronous. Barry may know more.

The added components could be someone's attempt to implement NAB eq.

rontech · 6th Nov 2018, 3:26 pm

The lathe needs to be in good condition, errors in concentricity between capstan bore and
the outer surface will manifest itself as wow & flutter

barrymagrec · 6th Nov 2018, 5:26 pm

I am not sure if I am the Barry referred to in #12 but as far as I know all Mk 5s had synchronous capstan motors, be they AEI or Papst.

I don`t know if the Papst and AEI motors ran at the same speed anyway as Papst had a fondness for 6 pole (1000rpm) motors if I remember correctly.

I am not sure how or even if Brenell catered for 60hHz operation but I would have assumed it would be by changing the stepped motor pulley rather than either of the capstan sleeves.

Whether or not you machine the capstan sleeve or the motor pulley the point above about concentricity is well made. If I were making either I would first machine the bore to the correct dimension and then machine a mandrel to mount the piece on and finish the O.D. - easy enough for a competent machinist.

Everything I vaguely remember about Brenell tape machines relates to a period over forty years ago.

Earczar · 6th Nov 2018, 11:16 pm

Good point, on just changing the pulley. Thats how any Teac motor ive worked on had with the 60-50hrtz motor option. Well thanks for all the speed tips.
Next step is rebuilding this thing. Im getting a better handle on this model. It usually takes me awhile to start processing the schematics but im getting there slowly.

5th Nov 2018, 2:27 pm	#2
wd40addict Octode Join Date: May 2009 Location: Stevenage, Herts. UK. Posts: 1,518	Re: Brenell Mk5 M These values don't correspond to anything I can find on the schematics. What is the function of the switch they connect to? If you've imported the machine from the UK I assume you know the speed will be wrong unless it's a 60Hz version?

5th Nov 2018, 4:35 pm	#3
Earczar Retired Dormant Member Join Date: Oct 2018 Location: London, Ontario, Canada Posts: 7	Re: Brenell Mk5 M I thought the same thing with the values. After seeing other pictures this one must be modified. The heads are not that fantastic, i think ill strip it down and rebuild it as a preamp. The switch that they are on is to change the speed. Theres other loose connection i cant trace as well. I took a chance and unfortunately this will be a bigger project then expected. I do have a step up transformer but that wont solve my speed problem right? Unless i just run it at 11.75 ips or whatever it will roll at and only playback on same deck.

5th Nov 2018, 7:28 pm	#4
rontech Heptode Join Date: Jun 2017 Location: Southport, Merseyside, UK. Posts: 646	Re: Brenell Mk5 M I had a Brenell Mk 5 in the early 1960's I seem to remember the capstan sleeve was brass and removeable, with the large one for 3.5, 7, 15 i.p.s and a smaller one for 1 7/8 3.5 and 7 i.ps. If you know somebody with a good precision lathe, then suitable diameter capstans in brass may correct for the difference 60 hz / 50 Hz. __________________ Time flies like an arrow, fruit flies like a banana

5th Nov 2018, 8:53 pm	#5
vidjoman Dekatron Join Date: Jun 2013 Location: East Sussex, UK. Posts: 3,326	Re: Brenell Mk5 M They were available in those days direct from Brenell, so easy to replicate. The switch you referred to changes the equalisation of the amplifier to suit the ‘speed’ of the deck. It doesn’t change the speed, which is on the main deck.

5th Nov 2018, 10:35 pm	#6
Earczar Retired Dormant Member Join Date: Oct 2018 Location: London, Ontario, Canada Posts: 7	Re: Brenell Mk5 M I have both speed sleeves. Anyone know the size to replicate a 60hrtz motor. And yes they are definitely brass. Its possible i could get someone i used to work with to fix it on the lathe. Im starting to feel hope again on this deck. Thanks everyone for the advice.

2nd Nov 2018, 8:22 pm	#1
Earczar Retired Dormant Member Join Date: Oct 2018 Location: London, Ontario, Canada Posts: 7	Brenell Mk5 M Hi everyone this is my first post, im looking for some help trying to identify where a few components that need to be re-soldered. It took a long journey to Canada from the UK, so i hardly blame it letting go. It seems untouched but who knows? Im going to do a full recap eventually but want to have it in order first. The first resistor is 180kohm and the second says 350pF. The 350 has a flat connection so it should have been easy to spot but im totally stumped. Also they are both connected to the middle wafer. Attached Thumbnails

6th Nov 2018, 10:02 am	#7
rontech Heptode Join Date: Jun 2017 Location: Southport, Merseyside, UK. Posts: 646	Re: Brenell Mk5 M I imagine that a 50Hz motor will run fast by 6/5 (i.e. x 1.2 ) on North American 60 Hz supply. The tape speed will be defined by capstan circumferences per second. (pi x d) i.ps. where d is capstan diameter in inches. pi = 3.142 for practical purposes. I think the above is correct; it is 60 yrs since passing my 6th form math's exam. __________________ Time flies like an arrow, fruit flies like a banana Last edited by rontech; 6th Nov 2018 at 10:04 am. Reason: typo

6th Nov 2018, 10:40 am	#8
Stevie342000 Hexode Join Date: Jan 2006 Location: Greater Manchester, UK. Posts: 373	Re: Brenell Mk5 M If I recall correctly the standard size of the capstan sleeves is 1/2" and 1". You could always measure them with calipers.

6th Nov 2018, 11:26 am	#10
Earczar Retired Dormant Member Join Date: Oct 2018 Location: London, Ontario, Canada Posts: 7	Re: Brenell Mk5 M I'll deffinately measure them up with calipers, they look close to 1/2 and 1". Thanks for the math lesson Rontech. This is my first over the pond attempt if that is not already clearly obvious....lol

6th Nov 2018, 11:34 am	#11
vidjoman Dekatron Join Date: Jun 2013 Location: East Sussex, UK. Posts: 3,326	Re: Brenell Mk5 M I would suggest that you keep the originals and get new ones made. You’ll have the originals for reference.

6th Nov 2018, 2:14 pm	#12
wd40addict Octode Join Date: May 2009 Location: Stevenage, Herts. UK. Posts: 1,518	Re: Brenell Mk5 M My small capstan was slightly under 0.5", about 0.495" from memory, but my machine has the Pabst motor. It's possible the earlier AEI based models had the slightly larger diameter as I don't believe that motor was fully synchronous. Barry may know more. The added components could be someone's attempt to implement NAB eq.

6th Nov 2018, 3:26 pm	#13
rontech Heptode Join Date: Jun 2017 Location: Southport, Merseyside, UK. Posts: 646	Re: Brenell Mk5 M The lathe needs to be in good condition, errors in concentricity between capstan bore and the outer surface will manifest itself as wow & flutter __________________ Time flies like an arrow, fruit flies like a banana

6th Nov 2018, 5:26 pm	#14
barrymagrec Octode Join Date: Dec 2017 Location: Morden, Surrey, UK. Posts: 1,558	Re: Brenell Mk5 M I am not sure if I am the Barry referred to in #12 but as far as I know all Mk 5s had synchronous capstan motors, be they AEI or Papst. I don`t know if the Papst and AEI motors ran at the same speed anyway as Papst had a fondness for 6 pole (1000rpm) motors if I remember correctly. I am not sure how or even if Brenell catered for 60hHz operation but I would have assumed it would be by changing the stepped motor pulley rather than either of the capstan sleeves. Whether or not you machine the capstan sleeve or the motor pulley the point above about concentricity is well made. If I were making either I would first machine the bore to the correct dimension and then machine a mandrel to mount the piece on and finish the O.D. - easy enough for a competent machinist. Everything I vaguely remember about Brenell tape machines relates to a period over forty years ago. Last edited by barrymagrec; 6th Nov 2018 at 5:44 pm.

6th Nov 2018, 11:16 pm	#15
Earczar Retired Dormant Member Join Date: Oct 2018 Location: London, Ontario, Canada Posts: 7	Re: Brenell Mk5 M Good point, on just changing the pulley. Thats how any Teac motor ive worked on had with the 60-50hrtz motor option. Well thanks for all the speed tips. Next step is rebuilding this thing. Im getting a better handle on this model. It usually takes me awhile to start processing the schematics but im getting there slowly.